ORIGINAL ARTICLE
Just-in-Time Adaptive Interventions (JITAIs) in Mobile Health:
Key Components and Design Principles for Ongoing Health
Behavior Support
Inbal Nahum-Shani, PhD
1
& Shawna N. Smith, PhD
2
& Bonnie J. Spring, PhD
3
&
Linda M. Collins, PhD
4
& Katie Witkiewitz, PhD
5
& Ambuj Tewari, PhD
6
&
Susan A. Murphy, PhD
7
#
The Society of Behavioral Medicine 2016
Abstract
Background The just-in-time adaptive intervention (JITAI) is
an intervention design aiming to provide the right
type/amount of support, at the right time, by adapting to an
individual’s changing internal and contextual state. The avail-
ability of increasingly powerful mobile and sensing technolo-
gies underpins the use of JITAIs to support health behavior, as
in such a setting an individual’s state can change rapidly, un-
expectedly, and in his/her natural environment.
Purpose Despite the increasing use and appeal of JITAIs, a
major gap exists between the growing technological capabil-
ities for delivering JITAIs and research on the development
and evaluation of these interventions. Many JITAIs have been
developed with minimal use of empirical evidence, theory, or
accepted treatment guidelines. Here, we take an essential first
step towards bridging this gap.
Methods Building on health behavior theories and the extant
literature on JITAIs, we clarify the scientific motivation for
JITAIs, define their fundamental components, and highlight
design principles related to these components. Examples of
JITAIs from various domains of health behavior research are
used for illustration.
Conclusion As we enter a new era of technological capacity
for delivering JITAIs, it is critical that researchers develop
sophisticated and nuanced health behavior theories capable
of guiding the construction of such interventions. Particular
attention has to be given to better understanding the implica-
tions of providing timely and ecologically sound support for
intervention adherence and retention.
Keywords Just-in-time adaptive intervention
.
Support
.
Mobile health (mHealth)
.
Health behavior
Introduction
An emerging intervention design, the just-in-time adaptive
intervention (JITAI) holds enormous potential for promoting
health behavior change. A JITAI is an intervention design that
adapts the provision of support (e.g., the type, timing, intensi-
ty) “over time to an individual’s changing status and con-
texts,” with the goal to deliver support “at the moment and
in the context that the person needs it most and is most likely
to be receptive” [1]. Increasingly powerful mobile and sensing
technologies underpin this intervention design [2]. They allow
us to monitor the dynamics of an individual’s internal state
and context in real time and offer support flexibly in terms of
time and location [3]. JITAIs are increasingly being used to
* Inbal Nahum-Shani
Inbal@umich.edu
1
Institute for Social Research, University of Michigan, Ann
Arbor, MI, USA
2
Division of General Medicine, Department of Internal Medicine and
Institute for Social Research, University of Michigan, Ann
Arbor, MI, USA
3
Feinberg School of Medicine, Northwestern University,
Evanston, IL, USA
4
The Methodology Center and Department of Human Development &
Family Studies, Penn State, State College, PA, USA
5
Department of Psychology, University of New Mexico,
Albuquerque, NM, USA
6
Department of Statistics and Department of EECS, University of
Michigan, Ann Arbor, MI, USA
7
Department of Statistics, and Institute for Social Research, University
of Michigan, Ann Arbor, MI, USA
ann. behav. med.
DOI 10.1007/s12160-016-9830-8
support health behavior changes in domains such as physical
inactivity [4], alcohol use [5], mental illness [6], smoking [7],
and obesity [8]. Despite JITAIs’ increasing use and appeal,
research on their development and evaluation is in its early
stages. Many JITAIs have been developed with little empirical
evidence, theory, or accepted treatment guidelines [9].
To close the gap between the growing technical capabilities
to deliver JITAIs and an understanding of their scientific under-
pinnings, it is important to clarify why JITAIs are needed and
how their objectives differ from those of other intervention de-
signs. This will help scientists build the empirical basis neces-
sary to develop efficacious JITAIs and decide whether a JITAI
is warranted in a particular setting [10]. Further, JITAI develop-
ment requires multidisciplinary effort, involving clinicians, be-
havioral scientists, engineers, statisticians, computer scientists,
and human-computer interaction specialists. A unified lexicon
can help to foster communication ac r oss diverse perspectives
and facilitate better collaboration and scientific exchange [2].
Finally, because JITAIs are multi-component interventions, it is
important to clearly define the components that comprise them,
so that investigators can attend to the utility of each component.
Investigating the effectiveness of each component and how well
different components work together is critical in the process of
optimizing a multi-component intervention [11].
In this article, we clarify the scientific motivation for JITAIs,
define their key components, and highlight important design
principles relevant to these components. We also discuss empir-
ical, theoretical, and practical challenges for constructing effica-
cious JITAIs. We ground our discussion by providing examples
of JITAIs from various domains of health behavior research.
Table 1 provides a summary of key terms and definitions.
Examples of JITAIs
JITAIs have been implemented and pilot tested in several do-
mains of health behavior change. For example, FOCUS [15] is
a smartphone behavioral intervention that provides illness
management support to individuals with schizophrenia.
FOCUS prompts individuals three times a day (via auditory
signals and visual notifications) to assess their status in five
target domains: medication adherence, mood regulation,
sleep, social functioning, and coping with hallucinations.
Once signaled, individuals can engage or ignore the prompt.
If they engage, the system launches a brief assessment. When
an assessment indicates that the individual is experiencing
difficulties, FOCUS recommends self-management strategies
to ameliorate the type of difficulties the individual endorsed;
otherwise, FOCUS provides feedback and positive reinforce-
ment. No intervention is offered if the individual ignores the
prompt.
ACHESS [5] is a JITAI for supporting recovery from alco-
hol use disorders. It provides 24-7 access via smartphone to a
wide variety of supportive services, including computerized
cognitive-behavioral therapy, web-links to addiction-related
websites, and information on alcohol-free events in their com-
munity. Global positioning system (GPS) technology tracks
when an individual approaches a high-risk location, namely a
location that the individual pre-specified as a place where s/he
regularly obtained or consumed alcohol in the past (e.g., fa-
vorite bar). If the individual approaches a high-risk location,
ACHESS sends an alert to the individual asking him/her if
s/he wanted to be there; otherwise, no alerts are delivered.
Finally, SitCoach [16] i s a JITAI for office workers in
which messages encouraging activity are delivered via a
smartphone. Software on the worker’s computer records un-
interrupted computer time via mouse and keyboard activity. If
30 min of uninterrupted computer time occurs, the smartphone
delivers a persuasive message to raise the individual’s aware-
ness of his/her sedentary behavior and encourage a walking
activity; otherwise, no messages are delivered. SitCoach does
not deliver a message if the individual received a message in
the past 2 hours, even if s/he exceeds the computer activity
threshold during that time.
Motivation for Just-in-Time Adaptive Interventions
Various scientific fields have used different terms to describe
interventions that adapt the provision of support to an individ-
ual’s changing internal and contextual state. These include
dynamic tailoring [17], intelligent real-time therapy [18], and
dynamically and individually tailored ecological momentary
interventions [19]. Here, we use the term JITAI because it
integrates two concepts: “just-in-time” and “adaptive.”
Attending to these concepts sheds ligh t on the motivation
underpinning these interventions as well as the components
comprising them.
In various scientific fields, including manufacturing [20]
and education [21], the term “just-in-time support” is used to
describe an attempt to provide the right type (or amount) of
support, at the right time [22], namely neither too early nor too
late [23]. The motivation for this approach is grounded in the
idea that timing plays an important role in determining wheth-
er support provision will be beneficial. Timing is defined as
“the moment (a static reference point in time) at which a phe-
nomenon, process, or part of process starts or finishes” [24].
Timing onset and offset demarcates a state that reflects the
particular condition(s) that someone or something is in at a
particular point or period of time [24]. Here, the concept of
timing is largely event-based, in that the answer to the ques-
tion “when is the right time?” is defined by events or condi-
tions (e.g., when the individual approaches a high-risk loca-
tion) rather than by clock time (e.g., at 2 pm). Such events/
conditions are unexpected—they repeat irregularly, in a man-
ner that cannot be fully predicted [25]. For example, it is
ann. behav. med.
ann. behav. med. (2017) XX:446–462
DOI: DOI:10.1007/s12160-016-9830-8
ann. behav. med. (2018) 52:446–462
DOI:10.1007/s12160-016-9830-8
Published online: 12 December 2017
2017
This article is part of a special section on Behavior Change Intervention Development that appears in this issue
REGULAR ARTICLE
Downloaded from https://academic.oup.com/abm/article/52/6/446/4733473 by guest on 20 August 2022
ORIGINAL ARTICLE
Just-in-Time Adaptive Interventions (JITAIs) in Mobile Health:
Key Components and Design Principles for Ongoing Health
Behavior Support
Inbal Nahum-Shani, PhD
1
& Shawna N. Smith, PhD
2
& Bonnie J. Spring, PhD
3
&
Linda M. Collins, PhD
4
& Katie Witkiewitz, PhD
5
& Ambuj Tewari, PhD
6
&
Susan A. Murphy, PhD
7
#
The Society of Behavioral Medicine 2016
Abstract
Background The just-in-time adaptive intervention (JITAI) is
an intervention design aiming to provide the right
type/amount of support, at the right time, by adapting to an
individual’s changing internal and contextual state. The avail-
ability of increasingly powerful mobile and sensing technolo-
gies underpins the use of JITAIs to support health behavior, as
in such a setting an individual’s state can change rapidly, un-
expectedly, and in his/her natural environment.
Purpose Despite the increasing use and appeal of JITAIs, a
major gap exists between the growing technological capabil-
ities for delivering JITAIs and research on the development
and evaluation of these interventions. Many JITAIs have been
developed with minimal use of empirical evidence, theory, or
accepted treatment guidelines. Here, we take an essential first
step towards bridging this gap.
Methods Building on health behavior theories and the extant
literature on JITAIs, we clarify the scientific motivation for
JITAIs, define their fundamental components, and highlight
design principles related to these components. Examples of
JITAIs from various domains of health behavior research are
used for illustration.
Conclusion As we enter a new era of technological capacity
for delivering JITAIs, it is critical that researchers develop
sophisticated and nuanced health behavior theories capable
of guiding the construction of such interventions. Particular
attention has to be given to better understanding the implica-
tions of providing timely and ecologically sound support for
intervention adherence and retention.
Keywords Just-in-time adaptive intervention
.
Support
.
Mobile health (mHealth)
.
Health behavior
Introduction
An emerging intervention design, the just-in-time adaptive
intervention (JITAI) holds enormous potential for promoting
health behavior change. A JITAI is an intervention design that
adapts the provision of support (e.g., the type, timing, intensi-
ty) “over time to an individual’s changing status and con-
texts,” with the goal to deliver support “at the moment and
in the context that the person needs it most and is most likely
to be receptive” [1]. Increasingly powerful mobile and sensing
technologies underpin this intervention design [2]. They allow
us to monitor the dynamics of an individual’s internal state
and context in real time and offer support flexibly in terms of
time and location [3]. JITAIs are increasingly being used to
* Inbal Nahum-Shani
Inbal@umich.edu
1
Institute for Social Research, University of Michigan, Ann
Arbor, MI, USA
2
Division of General Medicine, Department of Internal Medicine and
Institute for Social Research, University of Michigan, Ann
Arbor, MI, USA
3
Feinberg School of Medicine, Northwestern University,
Evanston, IL, USA
4
The Methodology Center and Department of Human Development &
Family Studies, Penn State, State College, PA, USA
5
Department of Psychology, University of New Mexico,
Albuquerque, NM, USA
6
Department of Statistics and Department of EECS, University of
Michigan, Ann Arbor, MI, USA
7
Department of Statistics, and Institute for Social Research, University
of Michigan, Ann Arbor, MI, USA
ann. behav. med.
DOI 10.1007/s12160-016-9830-8
support health behavior changes in domains such as physical
inactivity [4], alcohol use [5], mental illness [6], smoking [7],
and obesity [8]. Despite JITAIs’ increasing use and appeal,
research on their development and evaluation is in its early
stages. Many JITAIs have been developed with little empirical
evidence, theory, or accepted treatment guidelines [9].
To close the gap between the growing technical capabilities
to deliver JITAIs and an understanding of their scientific under-
pinnings, it is important to clarify why JITAIs are needed and
how their objectives differ from those of other intervention de-
signs. This will help scientists build the empirical basis neces-
sary to develop efficacious JITAIs and decide whether a JITAI
is warranted in a particular setting [10]. Further, JITAI develop-
ment requires multidisciplinary effort, involving clinicians, be-
havioral scientists, engineers, statisticians, computer scientists,
and human-computer interaction specialists. A unified lexicon
can help to foster communication ac r oss diverse perspectives
and facilitate better collaboration and scientific exchange [2].
Finally, because JITAIs are multi-component interventions, it is
important to clearly define the components that comprise them,
so that investigators can attend to the utility of each component.
Investigating the effectiveness of each component and how well
different components work together is critical in the process of
optimizing a multi-component intervention [11].
In this article, we clarify the scientific motivation for JITAIs,
define their key components, and highlight important design
principles relevant to these components. We also discuss empir-
ical, theoretical, and practical challenges for constructing effica-
cious JITAIs. We ground our discussion by providing examples
of JITAIs from various domains of health behavior research.
Table 1 provides a summary of key terms and definitions.
Examples of JITAIs
JITAIs have been implemented and pilot tested in several do-
mains of health behavior change. For example, FOCUS [15] is
a smartphone behavioral intervention that provides illness
management support to individuals with schizophrenia.
FOCUS prompts individuals three times a day (via auditory
signals and visual notifications) to assess their status in five
target domains: medication adherence, mood regulation,
sleep, social functioning, and coping with hallucinations.
Once signaled, individuals can engage or ignore the prompt.
If they engage, the system launches a brief assessment. When
an assessment indicates that the individual is experiencing
difficulties, FOCUS recommends self-management strategies
to ameliorate the type of difficulties the individual endorsed;
otherwise, FOCUS provides feedback and positive reinforce-
ment. No intervention is offered if the individual ignores the
prompt.
ACHESS [5] is a JITAI for supporting recovery from alco-
hol use disorders. It provides 24-7 access via smartphone to a
wide variety of supportive services, including computerized
cognitive-behavioral therapy, web-links to addiction-related
websites, and information on alcohol-free events in their com-
munity. Global positioning system (GPS) technology tracks
when an individual approaches a high-risk location, namely a
location that the individual pre-specified as a place where s/he
regularly obtained or consumed alcohol in the past (e.g., fa-
vorite bar). If the individual approaches a high-risk location,
ACHESS sends an alert to the individual asking him/her if
s/he wanted to be there; otherwise, no alerts are delivered.
Finally, SitCoach [16] i s a JITAI for office workers in
which messages encouraging activity are delivered via a
smartphone. Software on the worker’s computer records un-
interrupted computer time via mouse and keyboard activity. If
30 min of uninterrupted computer time occurs, the smartphone
delivers a persuasive message to raise the individual’s aware-
ness of his/her sedentary behavior and encourage a walking
activity; otherwise, no messages are delivered. SitCoach does
not deliver a message if the individual received a message in
the past 2 hours, even if s/he exceeds the computer activity
threshold during that time.
Motivation for Just-in-Time Adaptive Interventions
Various scientific fields have used different terms to describe
interventions that adapt the provision of support to an individ-
ual’s changing internal and contextual state. These include
dynamic tailoring [17], intelligent real-time therapy [18], and
dynamically and individually tailored ecological momentary
interventions [19]. Here, we use the term JITAI because it
integrates two concepts: “just-in-time” and “adaptive.”
Attending to these concepts sheds ligh t on the motivation
underpinning these interventions as well as the components
comprising them.
In various scientific fields, including manufacturing [20]
and education [21], the term “just-in-time support” is used to
describe an attempt to provide the right type (or amount) of
support, at the right time [22], namely neither too early nor too
late [23]. The motivation for this approach is grounded in the
idea that timing plays an important role in determining wheth-
er support provision will be beneficial. Timing is defined as
“the moment (a static reference point in time) at which a phe-
nomenon, process, or part of process starts or finishes” [24].
Timing onset and offset demarcates a state that reflects the
particular condition(s) that someone or something is in at a
particular point or period of time [24]. Here, the concept of
timing is largely event-based, in that the answer to the ques-
tion “when is the right time?” is defined by events or condi-
tions (e.g., when the individual approaches a high-risk loca-
tion) rather than by clock time (e.g., at 2 pm). Such events/
conditions are unexpected—they repeat irregularly, in a man-
ner that cannot be fully predicted [25]. For example, it is
ann. behav. med.
ann. behav. med. (2018) 52:446–462 447
Downloaded from https://academic.oup.com/abm/article/52/6/446/4733473 by guest on 20 August 2022
impossible to anticipate exactly when the individual will ap-
proach a high-risk location. Hence, ongoing monitoring of the
individual is required in order to identify when these events/
conditions occur (i.e., when support is needed).
The right time to pro vide support is determined by the
theory of change that is guiding support provision, namely
how and why a desired change is expected to unfold over time
in a particular context [26]. The flip-side of providing the right
type of support at the right time is providing nothing when the
time is wrong and never providing the wrong type of support
[27]. This operationalizes the notion of eliminating waste,
namely any activity/action that absorbs resources (e.g., time,
effort) but adds no value to, or even disrupts the desired pro-
cess [28].
Adaptation operationalizes how the provision of just-in-
time support will be accomplished [29, 30]. Adaptation is
defined as the use of ongoing (dynamic) information about
the individual to modify the type, amount, and timing of sup-
port [31]. To provide support just-in-time, the adaptation re-
quires monitoring the individual to decide (a) whether the
individual is in a state that requires support; (b) what type
(or amount) of support is needed given the individual’s state;
and (c) whether providing this support has the potential to
disrupt the desired process.
In the context of health behavior interventions, the use of
mobile technology to deliver just-in-time support is rooted in
theoretical and practical perspectives suggesting that states of
vulnerability to adverse health events, as well states of
Table 1 Key terms and
definitions
Key term Definition
Intervention design The approach and specifics of an intervention program.
Just-in-time support Attempts to provide the right type of support, at the right time, while
eliminating support provision that is interruptive or otherwise not
beneficial
Individualization The use of information from the individual to select when and how to
intervene.
Adaptation A dynamic form of individualization, whereby time-varying (dynamic)
information from the person is used repeatedly to select intervention
options over time.
Just-in-time adaptive
intervention (JITAI)
An intervention design aiming to provide just-in-time support, by
adapting to the dynamics of an individual’s internal state and context.
JITAIs operationalize the individualization of the selection and
delivery of intervention options based on ongoing assessments of
the i ndividual’s internal state and context. A JITAI includes 6 key
elements: a distal outcome, proximal outcomes, decision points,
intervention options, tailoring variables, and decision rules.
State of vulnerability/opportunity A period of susceptibility to negative health outcomes (vulnerability)
or to positive health behavior changes (opportunity).
Distal outcome The ultimate goal the intervention is intended to achieve; usually a
primary clinical outcome such as time to drug use/relapse or physical
activity level.
Proximal outcomes The short-term goals the intervention is intended to achieve. Proximal
outcomes can be mediators, namely crucial elements in a pathway
through which the intervention can impact the distal outcome,
and/or intermediate measures of the distal outcome.
Decision points Points in time at which an intervention decision must be made.
Tailoring variables Information concerning the individual that is used for individualization
(i.e., to decide when and/or how to intervene).
Intervention options Array of possible treatments/actions that might be employed at any
given decision point. This might include various types of support,
from various sources, different modes of support delivery, various
amounts of support or different media deployed for support delivery.
Decision rules A way to operationalize the adaptation by specifying which intervention
option to offer, for whom, and when (i.e., under which
experiences/contexts). The decision rules link the intervention
options and tailoring variables in a systematic way.
Intervention engagement A “state of motivational commitment or investment in the client role
over the treatment process” [12].
Intervention fatigue A state of emotional or cognitive weariness associated with intervention
engagement [13].
ann. behav. med.
opportunity for positive changes, can emerge rapidly (e.g.,
over a few days, hours, minutes, even seconds [32–34]); un-
expectedly (i.e., in an irregular manner [35]); and outside of
standard treatment settings (for review, see [36]).
States of Vulnerability and States of Opportunity
Theories that focus on preventing adverse health outcomes,
such as stress-vulnerability [37] and relapse prevention [38]
theories, highlight the importance of properly addressing
states of vulnerability, namely periods of heightened suscep-
tibility to negative health outcomes (e.g., unhealthy eating,
heavy drinking). The emergence of a vulnerable state is a
dynamic process in which stable and transient influences in-
teract. Stable factors refer to enduring predisposing influences,
including both internal (e.g., personality, genetics) and con-
textual (e.g., neighborhood safety, unemployment) factors that
increase the odds that a person will experience an adverse
health outcome at some point in his/her life. In turn, transient
influences precipitate a transition in vulnerability from latent
(subthreshold) to manifest. Transient precipitating influences
can be both internal (e.g., how the person is feeling) and con-
textual (e.g., location) [37, 38]. A vulnerable state can emerge
rapidly, unexpectedly, and in the individual’s natural environ-
ment, as s/he encounters circumstances that precipitate his/her
longstanding vulnerability [39]. These precipitating circum-
stances can vary between people and within a person over
time [32]. The JITAI aims to contain the vulnerable state and
return the condition of vulnerability to latent.
One example of a JITAI that aims to address a vulnerable
state is FOCUS, which was motivated by evidence suggesting
that transient difficulties play an important role (along with
stable factors such as biological predisposition) in the course
and outcomes of schizophrenia. Specifically, difficulties such
as fatigue and interpersonal conflict precipitate a transition to a
state of vulnerability that signifies the patient’s increasing risk
for full symptomatic relapse and illness exacerbation. These
difficulties can emerge rapidly, unexpectedly, and outside of
standard treatment settings. Further, these difficulties can take
different forms across individuals or even in the same individ-
ual over time. For example, psychotic episodes might be trig-
gered mainly by states of fatigue for some individuals and by
interpersonal conflict for others. Moreover, the individual may
be susceptible to relapse because s/he is experiencing sleep
difficulties at one time, and at another time because s/he forgot
to take his/her medication. Hence, FOCUS aims to provide the
type of support needed to help the individual cope with the
difficulties s/he is experiencing, at the right time to break the
link between these precipitating circumstances, the emergence
of the vulnerable state, and its progression into full symptom-
atic relapse.
JITAIs are also motivated by the importance of capitalizing
on states of opportunity, namely periods of heightened
susceptibility to positive health behavior changes (e.g.,
healthy eating, physical activity) [33, 34]. For instance, health
behavior maintenance perspectives emphasize the importance
of anticipatory coping [40]—a dynamic process involving on-
going anticipation of difficulties and timely execution of the
right strategy to prevent and/or minimize temptation (e.g., a
dieter keeping healthy food in the refrigerator [39, 41]). Health
behavior motivation theories suggest that it is important to
break long-term health behavior goals into short-term, specif-
ic, and achievable sub-goals; monitor progress; and provide
relevant, timely feedback and guidance [35, 42]. Learning and
cognitive theories emphasize the role of shaping (i.e., identi-
fying and immediately reinforcing successively improving ap-
proximations of the target behavior [43, 44]) and teachable
moments (i.e., natural opportunities for learning and improve-
ment [45, 46]) in the acquisition of a new skill. Overall, these
perspectives emphasize that timely provision of intervention
scaffolds and prompts can capitalize on short-term natural
opportunities to improve health outcomes. For example,
SitCoach is motivated by evidence suggesting that the occur-
rence of 30 min of uninterrupted computer use constitutes a
teachable moment that can be framed to raise an office
worker’s awareness of his/her sedentarism. To capitalize on
this opportunity, when 30 min of sedentary behavior occurs,
SitCoach provides feedback and persuasive messages to en-
courage the worker to be more active.
Because states of vulnerability and/or opportunity can
emerge rapidly, unexpectedly, and ecologically (i.e., in the
individual’s natural environment), it is usually infeasible to
use in-person (face-to-face) approaches to identify the time
when support is needed and to deliver the right type of support
in a timely manner. Hence, the provision of just-in-time sup-
port in health behavior interventions relies heavily on the use
of mobile and wireless devices (mHealth) [47]. The wide-
spread use of technologies including smartphones, laptops,
and tablets enables individuals to access or receive interven-
tions anytime and anywhere [48]. Moreover, the portable na-
ture of wearable and ubiquitous computing sensors (e.g.,
wearable activity monitors, smartwatches), mobile-phone-
based sensing (e.g., accelerometry, GPS), digital footprints
(e.g., social media interactions, digital calendars), and low-
effort self-reporting (e.g., ecological momentary assessment
[EMA]) make it possible to monitor individuals continuously
and hence to know when and why a state of vulnerability/
opportunity emerges [49]. Even so, new challenges to inter-
vention adherence and retention arise.
New Challenges to Intervention Adherence and Retention
Newly recognized challenges to intervention adherence and
retention concern the use of mHealth to address states that
emerge rapidly, unexpectedly, and ecologically [19]. First, be-
cause states of vulnerability/opportunity can occur repeatedly
ann. behav. med.
448 ann. behav. med. (2018) 52:446–462
Downloaded from https://academic.oup.com/abm/article/52/6/446/4733473 by guest on 20 August 2022
impossible to anticipate exactly when the individual will ap-
proach a high-risk location. Hence, ongoing monitoring of the
individual is required in order to identify when these events/
conditions occur (i.e., when support is needed).
The right time to pro vide support is determined by the
theory of change that is guiding support provision, namely
how and why a desired change is expected to unfold over time
in a particular context [26]. The flip-side of providing the right
type of support at the right time is providing nothing when the
time is wrong and never providing the wrong type of support
[27]. This operationalizes the notion of eliminating waste,
namely any activity/action that absorbs resources (e.g., time,
effort) but adds no value to, or even disrupts the desired pro-
cess [28].
Adaptation operationalizes how the provision of just-in-
time support will be accomplished [29, 30]. Adaptation is
defined as the use of ongoing (dynamic) information about
the individual to modify the type, amount, and timing of sup-
port [31]. To provide support just-in-time, the adaptation re-
quires monitoring the individual to decide (a) whether the
individual is in a state that requires support; (b) what type
(or amount) of support is needed given the individual’s state;
and (c) whether providing this support has the potential to
disrupt the desired process.
In the context of health behavior interventions, the use of
mobile technology to deliver just-in-time support is rooted in
theoretical and practical perspectives suggesting that states of
vulnerability to adverse health events, as well states of
Table 1 Key terms and
definitions
Key term Definition
Intervention design The approach and specifics of an intervention program.
Just-in-time support Attempts to provide the right type of support, at the right time, while
eliminating support provision that is interruptive or otherwise not
beneficial
Individualization The use of information from the individual to select when and how to
intervene.
Adaptation A dynamic form of individualization, whereby time-varying (dynamic)
information from the person is used repeatedly to select intervention
options over time.
Just-in-time adaptive
intervention (JITAI)
An intervention design aiming to provide just-in-time support, by
adapting to the dynamics of an individual’s internal state and context.
JITAIs operationalize the individualization of the selection and
delivery of intervention options based on ongoing assessments of
the i ndividual’s internal state and context. A JITAI includes 6 key
elements: a distal outcome, proximal outcomes, decision points,
intervention options, tailoring variables, and decision rules.
State of vulnerability/opportunity A period of susceptibility to negative health outcomes (vulnerability)
or to positive health behavior changes (opportunity).
Distal outcome The ultimate goal the intervention is intended to achieve; usually a
primary clinical outcome such as time to drug use/relapse or physical
activity level.
Proximal outcomes The short-term goals the intervention is intended to achieve. Proximal
outcomes can be mediators, namely crucial elements in a pathway
through which the intervention can impact the distal outcome,
and/or intermediate measures of the distal outcome.
Decision points Points in time at which an intervention decision must be made.
Tailoring variables Information concerning the individual that is used for individualization
(i.e., to decide when and/or how to intervene).
Intervention options Array of possible treatments/actions that might be employed at any
given decision point. This might include various types of support,
from various sources, different modes of support delivery, various
amounts of support or different media deployed for support delivery.
Decision rules A way to operationalize the adaptation by specifying which intervention
option to offer, for whom, and when (i.e., under which
experiences/contexts). The decision rules link the intervention
options and tailoring variables in a systematic way.
Intervention engagement A “state of motivational commitment or investment in the client role
over the treatment process” [12].
Intervention fatigue A state of emotional or cognitive weariness associated with intervention
engagement [13].
ann. behav. med.
opportunity for positive changes, can emerge rapidly (e.g.,
over a few days, hours, minutes, even seconds [32–34]); un-
expectedly (i.e., in an irregular manner [35]); and outside of
standard treatment settings (for review, see [36]).
States of Vulnerability and States of Opportunity
Theories that focus on preventing adverse health outcomes,
such as stress-vulnerability [37] and relapse prevention [38]
theories, highlight the importance of properly addressing
states of vulnerability, namely periods of heightened suscep-
tibility to negative health outcomes (e.g., unhealthy eating,
heavy drinking). The emergence of a vulnerable state is a
dynamic process in which stable and transient influences in-
teract. Stable factors refer to enduring predisposing influences,
including both internal (e.g., personality, genetics) and con-
textual (e.g., neighborhood safety, unemployment) factors that
increase the odds that a person will experience an adverse
health outcome at some point in his/her life. In turn, transient
influences precipitate a transition in vulnerability from latent
(subthreshold) to manifest. Transient precipitating influences
can be both internal (e.g., how the person is feeling) and con-
textual (e.g., location) [37, 38]. A vulnerable state can emerge
rapidly, unexpectedly, and in the individual’s natural environ-
ment, as s/he encounters circumstances that precipitate his/her
longstanding vulnerability [39]. These precipitating circum-
stances can vary between people and within a person over
time [32]. The JITAI aims to contain the vulnerable state and
return the condition of vulnerability to latent.
One example of a JITAI that aims to address a vulnerable
state is FOCUS, which was motivated by evidence suggesting
that transient difficulties play an important role (along with
stable factors such as biological predisposition) in the course
and outcomes of schizophrenia. Specifically, difficulties such
as fatigue and interpersonal conflict precipitate a transition to a
state of vulnerability that signifies the patient’s increasing risk
for full symptomatic relapse and illness exacerbation. These
difficulties can emerge rapidly, unexpectedly, and outside of
standard treatment settings. Further, these difficulties can take
different forms across individuals or even in the same individ-
ual over time. For example, psychotic episodes might be trig-
gered mainly by states of fatigue for some individuals and by
interpersonal conflict for others. Moreover, the individual may
be susceptible to relapse because s/he is experiencing sleep
difficulties at one time, and at another time because s/he forgot
to take his/her medication. Hence, FOCUS aims to provide the
type of support needed to help the individual cope with the
difficulties s/he is experiencing, at the right time to break the
link between these precipitating circumstances, the emergence
of the vulnerable state, and its progression into full symptom-
atic relapse.
JITAIs are also motivated by the importance of capitalizing
on states of opportunity, namely periods of heightened
susceptibility to positive health behavior changes (e.g.,
healthy eating, physical activity) [33, 34]. For instance, health
behavior maintenance perspectives emphasize the importance
of anticipatory coping [40]—a dynamic process involving on-
going anticipation of difficulties and timely execution of the
right strategy to prevent and/or minimize temptation (e.g., a
dieter keeping healthy food in the refrigerator [39, 41]). Health
behavior motivation theories suggest that it is important to
break long-term health behavior goals into short-term, specif-
ic, and achievable sub-goals; monitor progress; and provide
relevant, timely feedback and guidance [35, 42]. Learning and
cognitive theories emphasize the role of shaping (i.e., identi-
fying and immediately reinforcing successively improving ap-
proximations of the target behavior [43, 44]) and teachable
moments (i.e., natural opportunities for learning and improve-
ment [45, 46]) in the acquisition of a new skill. Overall, these
perspectives emphasize that timely provision of intervention
scaffolds and prompts can capitalize on short-term natural
opportunities to improve health outcomes. For example,
SitCoach is motivated by evidence suggesting that the occur-
rence of 30 min of uninterrupted computer use constitutes a
teachable moment that can be framed to raise an office
worker’s awareness of his/her sedentarism. To capitalize on
this opportunity, when 30 min of sedentary behavior occurs,
SitCoach provides feedback and persuasive messages to en-
courage the worker to be more active.
Because states of vulnerability and/or opportunity can
emerge rapidly, unexpectedly, and ecologically (i.e., in the
individual’s natural environment), it is usually infeasible to
use in-person (face-to-face) approaches to identify the time
when support is needed and to deliver the right type of support
in a timely manner. Hence, the provision of just-in-time sup-
port in health behavior interventions relies heavily on the use
of mobile and wireless devices (mHealth) [47]. The wide-
spread use of technologies including smartphones, laptops,
and tablets enables individuals to access or receive interven-
tions anytime and anywhere [48]. Moreover, the portable na-
ture of wearable and ubiquitous computing sensors (e.g.,
wearable activity monitors, smartwatches), mobile-phone-
based sensing (e.g., accelerometry, GPS), digital footprints
(e.g., social media interactions, digital calendars), and low-
effort self-reporting (e.g., ecological momentary assessment
[EMA]) make it possible to monitor individuals continuously
and hence to know when and why a state of vulnerability/
opportunity emerges [49]. Even so, new challenges to inter-
vention adherence and retention arise.
New Challenges to Intervention Adherence and Retention
Newly recognized challenges to intervention adherence and
retention concern the use of mHealth to address states that
emerge rapidly, unexpectedly, and ecologically [19]. First, be-
cause states of vulnerability/opportunity can occur repeatedly
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over time, providing support at the right time might suggest
frequent delivery of interventions [50]. Second, addressing
these states often requires the delivery of interventions in a
real-life setting where multiple demands compete for the indi-
vidual’s time and effort. Finally, to reduce costs and other
barriers to treatment (e.g., availability of therapists, stigma),
many mHealth interventions include minimal or no support
from clinicians or coaches (e.g., [51, 52]). This introduces
unique challenges to the extent that supportive accountability
(i.e., “implicit or explicit expectation that an individual may
be called upon to justify his/her actions or inactions” [53]) is
enhanced by the felt presence of another human being [53].
Indeed, various studies demonstrate the law of attrition [54]
in mHealth interventions, showing that individuals use
mHealth resources only a few times before abandoning them
[55, 56], even when they paid for these resources [57]. For
example, in a randomized control trial, Laing and colleagues
[58] compared a popular publically available app for weight
loss with usual care for overweight patients in a primary care
setting. Although individuals reported liking the app, use
dropped sharply after the first month. For example, the median
number of logins was eight in the first month and one in the
second month; the number of individuals who actually used
the app dropped by 64 % from month 1 to month 6. Hence,
JITAIs in mobile health are also motivated by the need to
accommodate relat ively rapid changes in key mechanisms
underlying intervention adherence and retention.
Intervention engagement and intervention fatigue are two
important mechanisms that affect adherence and retention.
Intervention engagement is defined as a “state of motivational
commitment or investment in the client role over the treatment
process” []. Intervention fatigue (i.e., burnout) is defined as a
state of emotional or cognitive weariness associated with in-
tervention engagement [13]. Empirical and theoretical evi-
dence suggests that both mechanisms are important in inter-
vention adherence and retention [14], and both might ebb and
flow over the course of treatment as a function of aspects
related to the intervention , the individual, and the context
[13, ]. For example, King and colleagues [] conceptualize
intervention engagement as a multifaceted affective, cogni-
tive, and behavioral state that ebbs and flows over time due
to factors related to the intervention (e.g., how treatment is
presented and delivered), the individual (e.g., attitudes to-
wards self and treatment), and the context (e.g., work/family
demands). Heckman and colleagues [13] conceptualize inter-
vention fatigue as a cognitive and emotional state that fluctu-
ates over time as a function of the interplay between interven-
tion burden (i.e., the demands of an intervention in terms of
time and effort), the general demands on the individual (e.g.,
daily life tasks related to work and family), the capacity of the
individual in terms of general resources (e.g., attention,
mood), and illness burden (i.e., symptoms such as pain,
craving).
Building on these ideas, and consistent with the notion of
waste elimination, various perspectives in supportive commu-
nication and ubiquitous computing [59–61] emphasize the
need to provide just-in-time support only when the person is
receptive. Here, receptivity is defined as the individual’s tran-
sient ability and/or willingness to receive, process, and utilize
just-in-time support; receptivity is a function of both internal
(e.g., mood) and contextual (e.g., location) factors [50]. For
example, in FOCUS, support was not offered if the individual
ignored the prompt for self-report (i.e., s/he is not receptive).
The underlying assumption is that providing support when the
person is not receptive will not be beneficial and may even
have negative implications on engagement with the interven-
tion and intervention fatigue [61, 62]. Receptivity might
change rapidly in the course of a day [61], and what consti-
tutes receptivity depends on the type (i.e., content, media
employed for delivery), amount, and timing of support pro-
vided [63]. For example, if a person is in a meeting s/he might
be receptive to an intervention delivered via a text message,
but not receptive to a phone call. When it is raining, a person
might be receptive to a recommendation to exercise indoors,
but not receptive to a recommendation to walk outside.
Summary of JITAI Definition and Scientific Motivation
A JITAI is an intervention design that employs adaptation to
operationalize the provision of just-in-time support, namely to
provide the right type (or amount) of support, at the right time,
while eliminating support provision that is not beneficial. The
use of mobile health (mHealth) in this setting is motivated by
the need to address states of vulnerability for adverse health
outcomes and/or capitalize on states of opportunity that
emerge rapidly, unexpectedly, and ecologically. These states
can vary between individuals and over time within an individ-
ual. Hence, addressing and/or capitalizing on these states in a
timely manner requires continuous, ecological monitoring of
an individual’s internal state and context to identify when and
how to intervene. Advances in portable and pervasive tech-
nologies make it possible to continuously monitor individuals,
as well as the timely delivery of support “in the wild.”
However, given the rapid, unexpected, and ecological nature
of these states, as well as the law of attrition [54] in mHealth
interventions, JITAIs in mobile health are also motivated by
the need to address relatively rapid changes in mechanisms
underlying adherence and retention.
Notice that the definition above emphasizes that the adap-
tation in a JITAI is employed by the intervention itself rather
than by the target individual. In other words, decisions
concerning when and how to provide support are based on
the intervention’s protocol. This intervention-determined ap-
proach is based on evidence suggesting that individuals are
often unable to recognize when states of vulnerability and/or
opportunity emerge [64, 65] and initiate the type of support
ann. behav. med.
needed to address these states in a timely manner [66, 67].
Hence, a JITAI employs adaptation to actively address these
states of vulnerability and/or opportunity. We distinguish this
from participant-determined approaches that make an array of
supportive resources available for the target individual to de-
cide when and what type of support to initiate.
Components of a JITAI
JITAIs are adaptive interventions. An adaptive intervention is
an intervention design in which intervention options are
adapted to address the unique and changing needs of individ-
uals, with the goal of achieving the best outcome for each
individual [68]. Existing frameworks for the design of adap-
tive interventions [31] highlight four components that play an
important role in designing these interventions: (1) decision
points, (2) intervention options, (3) tailoring variables, and (4)
decision rules. Below, we describe each of these components
and how they might be employed in a JITAI. Figure 1 includes
a conceptual model of JITAI components.
Decision Points
A decision point is a time at which an intervention decision is
made. Given the nature of the conditions JITAIs in mobile
health attempt to address and the capabilities of modern tech-
nology, intervention decisions are made much more rapidly
than in standard adaptive interventions. For exampl e, in
FOCUS, intervention decisions were made following each
random prompt for self-report. An intervention was not nec-
essarily provided following every random prompt: if the indi-
vidual ignored the prompt (i.e., s/he was not receptive), no
intervention was offered. Table 2 includes other examples of
decision points in JITAIs. In general, the decision points in a
JITAI might occur (a) at a pre-specified time interval (e.g., the
location of a recovering individual is passively monitored ev-
ery minute to detect if/when s/he is approaching a high-risk
location [5]); (b) at specific times of day (e.g., at 2 pm) [73], or
days of the week [70]; or (c) following random prompts [15].
Intervention Options
Intervention options are an array of possible treatments or
actions that might be employed at any given decision point.
In JITAIs, these include various types of support (e.g., infor-
mation, advice, feedback), sources of support (e.g.,
smartphone, therapist), amounts of support (i.e.,
dose/intensity), or media employed to deliver support (e.g.,
phone calls, text messaging). For example, intervention op-
tions in FOCUS included both recommendations of self-
management strategies, as well as feedback and positive rein-
forcement. In a JITAI, intervention options are designed to be
delivered, accessed, and used in a timely and ecological man-
ner. The term ecological momentary interventions (EMIs) is
often used to describe intervention options that can be deliv-
ered and employed rapidly, as people go about their daily lives
[19].
Tailoring Variables
A tailoring variable is information concerning the individual
that is used to decide when (i.e., under what conditions) to
provide an intervention and which intervention to provide. For
example, in ACHESS, the tailoring variable is an individual’s
distance from a high-risk location. In a JITAI, the collection of
tailoring variables is flexible in terms of the timing and loca-
tion of assessments. This flexibility enables timely individu-
alization of intervention options to conditions that might
change rapidly, unexpectedly, and ecologically.
Tailoring variables in a JITAI can be obtained via active
assessments, passive assessments, or both [77]. Active
assessments, also known as EMAs, are self-reported and
hence require engagement on the part of the individual [78].
For example, in FOCUS, participants were prompted three
Fig. 1 Conceptual model of
JITAI components
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