Showing papers in "Journal of Psychopathology and Behavioral Assessment in 2004"

Multidimensional Assessment of Emotion Regulation and Dysregulation: Development, Factor Structure, and Initial Validation of the Difficulties in Emotion Regulation Scale

Abstract: Given recent attention to emotion regulation as a potentially unifying function of diverse symptom presentations, there is a need for comprehensive measures that adequately assess difficulties in emotion regulation among adults. This paper (a) proposes an integrative conceptualization of emotion regulation as involving not just the modulation of emotional arousal, but also the awareness, understanding, and acceptance of emotions, and the ability to act in desired ways regardless of emotional state; and (b) begins to explore the factor structure and psychometric properties of a new measure, the Difficulties in Emotion Regulation Scale (DERS). Two samples of undergraduate students completed questionnaire packets. Preliminary findings suggest that the DERS has high internal consistency, good test–retest reliability, and adequate construct and predictive validity.

Purpose in Life, Satisfaction With Life, and Suicide Ideation in a Clinical Sample

Abstract: This study examined the role of purpose in life and satisfaction with life in protecting against suicide ideation in a clinical psychiatric sample. Forty-nine psychiatric patients completed self-report measures of suicide ideation, purpose in life, satisfaction with life, neuroticism, depression, and social hopelessness. Zero-order correlations indicated significant associations between suicide ideation and the various predictors, in the hypothesized directions. Regression analyses illustrated that purpose in life and satisfaction with life accounted for significant additional variability in suicide ideation scores above and beyond that accounted for by the negative psychological factors alone. Purpose in life also mediated the relation between satisfaction with life and suicide ideation and moderated the relation between depression and suicide ideation. These findings demonstrate the potential value of attending to both resilience and pathology when building predictive models of suicide ideation and of attending to key existential themes when assessing and treating suicidal individuals.

Comparison of mothers', fathers', and teachers' reports on problem behavior in 5-to 6-year-old children

Abstract: Evidence exists that there is low agreement between multiple informants reporting on children's and adolescents' behavior problems Few studies, however, focus on agreement between informants in specific age groups This study examined correspondence and disagreement between mother, father, and teacher reports of problem behavior by analyzing CBCL and TRF data of 2 nonclinical samples of 5- to 6-year-old preschool children (N = 424) Findings indicated that interrater agreement was low to moderate This was shown by the intercorrelations, the explained variance in regression analyses and the little overlap in the number of children rated as behaviorally disturbed by all 3 informants Agreement between mother and father reports was highest, whereas agreement between mother and teacher reports was lowest Disagreement between informants was highest for internalizing problems Potential explanations for the lack of agreement are discussed Guidelines are formulated to refine assessment and optimize clinical decision-making processes

The Moral Disengagement Scale: Extension with an American Minority Sample

Abstract: This study extended an investigation by A. Bandura, C. Barbaranelli, G. V. Caprara, and C. Pastorelli (1996) by examining the structure, reliability, and correlates of the Moral Disengagement Scale (MDS), which measures disengagement from moral self-sanctions. Furthermore, the role of moral disengagement in the association between parenting and child behavior was examined. Two hundred and forty-five African American single-parent mothers and one of their children (mean age = 11.4 years) participated in the study. The MDS had similar factor structure, internal consistency, and demographic correlates as those reported by A. Bandura et al. (1996) with an Italian sample of children. The MDS also correlated with delinquent and aggressive child behavior, and moral disengagement partially mediated the relationship between parenting and child delinquent behavior.

A Multivariate Associative Finite Growth Mixture Modeling Approach Examining Adolescent Alcohol and Marijuana Use

Abstract: Theoretical and empirical substance use development research suggests that adolescent populations are not homogenous and can often be separated into subpopulations characterized by qualitatively different patterns of substance use development. This paper demonstrates the application of a multivariate associative finite latent growth mixture modelling approach to examine heterogeneity in patterns of adolescent alcohol and marijuana use and the influence of age, gender, parent, and peer substance use. Substance use problem outcomes were also examined. Participants were male and female adolescents (N = 1,044) ranging in age from 11 to 17 years at the first assessment (Mean age = 14.47; SD = 1.95). Individuals were 45% female and 82% Caucasian. Using growth mixture methodology, a 7-class model captured distinct simultaneous alcohol and marijuana use patterns over a 3-year period. Findings highlight the importance of examining subgroups of adolescent substance use, rather than focusing only on single samples.

Psychopathy and the Five Factor Model in a Noninstitutionalized Sample: A Domain and Facet Level Analysis

Abstract: The relationship of primary and secondary psychopathic dispositions as measured by the Levenson Self-Report Psychopathy (LSRP) Scales to NEO-PI-R domain and facet scales of the Five Factor Model (FFM) was examined in a sample (N = 463) of young adults. Previous investigations were extended by (1) addressing the relationship of higher- (i.e., domain) and lower-order (i.e., facet) FFM traits to primary and secondary psychopathy in noninstitutionalized persons, in an attempt to validate hypotheses by T. A. Widiger and D. R. Lynam (1998); (2) examining sex differences in FFM traits in relation to these two psychopathic dispositions; and (3) lending further evidence for the validity of the LSRP. LSRP primary psychopathy was marked by low Agreeableness whereas LSRP secondary psychopathy was characterized by high Neuroticism, low Agreeableness, and low Conscientiousness. Although few sex differences were found between primary and secondary psychopathy, findings support the use of NEO-PI-R domain and facet scales in the identification of personality disorder.

Evaluation of Two New Scales Assessing Driving Anger: The Driving Anger Expression Inventory and the Driver's Angry Thoughts Questionnaire

Abstract: This study assessed the validity of the Driving Anger Expression Inventory (DAX) and Driver's Angry Thoughts Questionnaire (DATQ). Scales within the DAX and DATQ appeared to assess separate, correlated constructs. Aggressive forms of thinking and anger expression correlated positively with each other, trait driving anger, aggressive and risky behavior, some crash-related conditions, general trait anger, and general forms of anger expression. Positive, constructive forms of thinking and anger expression correlated positively with each other, but minimally or negatively with other variables. Specific aggressive forms of thinking and anger expression formed stronger links with each other than other forms of expression, supporting the discriminant validity of the DATQ and DAX. Hierarchical regressions with DATQ and DAX scales entered after other variables showed that they added explained variance above and beyond other measures, supporting the discriminant and incremental validity of these scales. It was concluded that the DAX and DATQ have utility for researchers and clinicians interested in angry drivers.

Perfectionism as an Explanatory Construct in Comorbidity of Axis I Disorders

Abstract: Understanding comorbidity is an important challenge for psychopathology researchers and diagnostic systems given the repeated finding of very high comorbidity rates among Axis I disorders in psychiatric samples. This paper proposes that perfectionism may be a critical factor for understanding levels of comorbidity, and a conceptual argument for the importance of perfectionism as an explanatory construct for comorbidity is advanced. The link between perfectionism and comorbidity in a large sample of patients (N = 345) who attended an anxiety disorders clinic is examined using a variety of methods. Diagnoses were established using the Structured Clinical Interview for DSM-IV (SCID-IV), and perfectionism was assessed using both the Hewitt and Flett and Frost Multidimensional Perfectionism Scales. Overall, scores on both the Hewitt and Flett and Frost perfectionism scales were correlated with the number of diagnoses, and a logistic regression analysis, controlling for current symptoms, showed that maladaptive evaluative concerns perfectionism in particular predicted higher levels of comorbidity.

Differences in Individual and Dyadic Coping Among Low and High Depressed, Partially Remitted, and Nondepressed Persons

Abstract: Investigations of the individual and interpersonal coping resources of depressed persons are underrepresented in the field of research on depression. Whereas some studies have been conducted on depressed couples evaluating individual coping or social support from others, only a few studies have addressed the topic of dyadic coping, or the way both partners cope together. In the present effort, male and female participants with a current or past diagnosis of depression, all of whom were married or cohabiting in a close relationship, reported on their individual and dyadic coping and were compared on these variables with a matched group of control participants. Results corroborate previous findings on deficits in individual coping, and to a lesser degree in dyadic coping.

Global Maladaptive Schemas, Negative Life Events, and Psychological Distress

Abstract: The relationship between maladaptive self-schemas, negative life events, and psychological distress was assessed. The model tested was based on Young's (J. Young, 1990) diathesis–stress conceptualization of maladaptive schemas, which are believed to represent the cognitive diathesis underlying Axis II personality pathology. Young's model predicts that schemas are chronically activated in individuals with maladaptive schemas. Therefore, the experience of salient negative life events is less likely to exacerbate the level of distress experienced by those having maladaptive schemas. A nonclinical sample (N = 93) was assessed using the Schema Questionnaire (SQ), a measure of maladaptive self-schemas, a measure of negative life events, and several measures of psychological distress. Support was found for this prediction indicated by a Schema × Negative Life Events interaction in which the distress level of High SQ participants was less affected by negative life events compared to Low SQ participants.

Dimensionality of the Obsessive Beliefs Questionnaire (OBQ)

Abstract: The Obsessive Beliefs Questionnaire (OBQ) is a self-report measure in development by the Obsessive Compulsive Cognitions Working Group (OCCWG), who studies cognitive aspects of obsessive–compulsive disorder (OCD). The aim of this paper was to evaluate the dimensionality of the OBQ in students (n = 995). Two models were tested in a confirmatory framework, corresponding to the OCCWG's (a) original six subscales (87 items), and (b) more recent three subscales (44 items). Both models fit the present data poorly; thus, an exploratory analysis was undertaken. Results revealed one large factor that is relevant, but not unique, to OCD, and three factors that are conceptually consistent with the OCCWG's recent three: (a) distorted beliefs about one's own thoughts, (b) perfectionism, and (c) inflated responsibility. Convergent and divergent validity analyses of the present OBQ factors generally supported the preceding interpretations. Readers are referred to the work of the OCCWG for revisions to the OBQ.

Prevalence of Smoking in Anxiety Disorders Uncomplicated by Comorbid Alcohol or Substance Abuse

Abstract: This study examined the point prevalence of smoking in patients with anxiety disorders who do not have comorbid alcohol or substance abuse or dependence (ASAD). In a retrospective chart review, the smoking status of 581 patients with anxiety disorders was assessed. Patients, ages 18–65, were seeking treatment for anxiety disorders at an outpatient clinic that specialized in anxiety and related disorders. All participants were interviewed using the Anxiety Disorders Interview Schedule—IV, during which their smoking status was assessed. The prevalence of smoking across all anxiety disorders was 14.8%, which is much lower than found in the general population (23.3%; CDC, 2002) and even lower than previous estimates in individuals with comorbid anxiety and ASAD. Individuals with panic disorder and generalized anxiety disorder had the highest prevalence of smoking, although these rates were still considerably lower than those found in previous studies of smokers with anxiety disorders. Reasons for lower prevalence estimates are discussed.

Pretrauma Neuroticism, Negative Appraisals of Intrusions, and Severity of PTSD Symptoms

Abstract: Earlier studies found that self-reported posttraumatic stress disorder (PTSD) symptoms are correlated with negative appraisals of symptoms and with neuroticism. It is unclear whether the latter two are associated. Possibly, an overarching trait such as neuroticism mediates the relationship between PTSD symptoms and negative appraisals of symptoms. Data from a previous study (see I. M. Engelhard, M. A. van den Hout, M. Kindt, A. Arntz, & E. Schouten, 2003) were used in the present effort to address these issues. Neuroticism scores were obtained from 1,372 pregnant women. One hundred and twenty-six women experienced a pregnancy loss, and 117 of them were assessed for PTSD symptoms and negative appraisals of symptoms. The 3 variables of interest were all significantly correlated. The data indicate that negative appraisals of symptoms explain and predict PTSD symptoms independently of neuroticism.

Clinical Validation of the Swedish Version of the Quality of Life Inventory in Crime Victims With Posttraumatic Stress Disorder and a Nonclinical Sample

Abstract: The Swedish version of the Quality of Life Inventory (QOLI) was cross-culturally validated with a crime victim sample (N = 53) with posttraumatic stress disorder (PTSD) and a nonclinical group (N = 100) with no lifetime and current psychiatric disorder from the general population in the Stockholm county of Sweden. The QOLI showed excellent internal consistencies in the clinical and the nonclinical sample. In addition, PTSD participants displayed a significantly lower self-perceived quality of life in 13 out of 16 domains of life than the nonclinical individuals. Furthermore, the QOLI was inversely correlated with interview and self-report measures of PTSD symptoms, depression, and anxiety. Overall, the results support the utility of the Swedish QOLI version as a potentially useful measure of self-perceived quality of life in Swedish clinical and nonclinical samples. The results are discussed in relation to the Swedish cross-cultural validation of the QOLI, methodological limitations and future directions.

Structural Validation of the Hamilton Depression Rating Scale

Abstract: Despite the prolific use of the Hamilton Depression Rating Scale (HDRS), there have been no prior studies using confirmatory factor analysis (CFA) to compare competing HDRS latent structures. The current study undertakes this task, examining CFAs on 397 older adults on the most stable latent models previously posited and a new rationally derived model by Cole and Motivala. CFAs were evaluated in their original first-order structure and in hierarchically related counterparts. All hierarchical models performed significantly better than their first-order counterparts. Moreover, the hierarchical Cole and Motivala model was significantly better on all comparative criteria than any of the other models. However, none of the tested models obtained sufficient fit with the data suggesting psychometric, scoring, or content limitations of the scale.

Body-Focused Repetitive Behaviors: The Proximal and Distal Effects of Affective Variables on Behavioral Expression

Abstract: This paper reports on 2 studies designed to examine the contribution of affective variables on the expression of body-focused repetitive behaviors (BFRBs; e.g., skin picking, nail biting). The first study revealed that persons engaging in a BFRB experienced significantly higher levels of anxiety and depression than those without BFRBs. The second study was conducted to determine if repetitive behaviors were differentially affected across various emotional states and across those persons with and without BFRBs. Participants were randomly exposed to anxiety, depression, boredom, and control conditions. Results showed no differential effects on the occurrence of repetitive behaviors within the no-BFRB group; however, the BFRB group engaged in more repetitive behaviors in the Bored condition than in the Control condition. This study offers the first experimental evidence that emotional variables can have a differential impact on the expression of BFRBs.

The Psychophysiology of Orthostatic Panic in Cambodian Refugees Attending a Psychiatric Clinic

Abstract: Orthostatically triggered panic was examined in female Cambodian refugees. Heart rate, blood pressure (BP), panic, and dizziness responses were assessed during orthostatic challenge in three diagnostic groups: orthostatic panic without comorbid posttraumatic stress disorder (PTSD), orthostatic panic with PTSD, and other mental disorders without orthostatic panic or PTSD. During orthostatic challenge, the panic group without PTSD showed a significant drop, whereas the group with other mental disorders showed an increase in systolic BP. The group with panic and PTSD showed a blunted systolic BP response during orthostasis that fell between the responses of the other groups. Catastrophic, culturally specific cognitions present during orthostatic challenge were significantly correlated with the amount of reported panic upon standing. Some patients recalled previous traumatic events during the orthostatic challenge. The findings suggest that orthostatically induced panic attacks in Cambodian refugees are generated by an interaction of orthostasis physiology, catastrophic cognitions, and trauma associations.

Mood Regulation Skill and the Symptoms of Endogenous and Hopelessness Depression in Spanish High School Students

Abstract: To assess the construct validity of the endogenous subtype of depression, 2 studies examined the relation of mood regulation skill to the symptoms of endogenous depression versus hopelessness depression in adolescent samples. It was hypothesized that the relationship between mood regulation skill and endogenous depression would be weaker than the relationship between mood regulation skill and hopelessness depression, because endogenous depression may be less influenced by personality variables, such as mood regulation skill. In spite of the high degree of correlation between the symptoms of hopelessness depression and endogenous depression, the relationship between mood regulation skill and hopelessness depression was stronger than the relationship between mood regulation skill and endogenous depression, as predicted. This is consistent with proposed definition of endogenous depression.

Invited Special Review: Psychological Approaches for Managing Chronic Pain

Abstract: Psychologists have had an important impact on the conceptualization, assessment, and treatment of chronic pain. Their contributions have been in the areas of emotional distress, behavioral limitations, cognitive mediating events, and psychosocial disruption of chronic pain. These foci have enabled them to clarify the multidimensional nature of chronic pain and to support the biopsychosocial framework as a conceptual guide for research and clinical purposes. Clinically, along with members of an interdisciplinary team, psychologists have a key role in the assessment and treatment of patients with chronic pain. Interdisciplinary collaboration allows the team to recognize important interactions between biomedical and psychosocial dimensions and to appreciate a broader conceptualization of patients' problems. The literature documents strong empirical support for operant-behavioral and cognitive-behavioral therapies for the treatment of chronic pain. On the other hand, although widely accepted from a clinical perspective, the use of motivational interviewing and motivational enhancement therapies is more recent and less well documented for use with patients with chronic pain.

A Latent Growth Curve Modeling Approach to Pooled Interrupted Time Series Analyses

Abstract: This paper presents a latent variable approach for the estimation of treatment effects within a pooled interrupted time series (ITS) design. Although considered quasi-experimental, the ITS design has been noted as representing one of the strongest alternatives to the randomized experiment, making it highly appropriate for use in documenting the presence of effects that might warrant further evaluation in a large-scale randomized study. Results suggest that the latent variable growth modeling (LGM) is capable of detecting simultaneous differences in both level and slope, and provides tests of significance for these two necessary indicators of an ITS intervention effect. As shown in the analyses, the LGM framework provides a comprehensive and flexible approach to research design and data analysis, making available to a wide audience of researchers an analytical framework for a variety of analyses of growth and developmental processes.

Investigating the big five personality factors and smoking: Implications for assessment

Abstract: Global personality dispositions may be important for understanding population-based individual differences in smoking outcomes, yet few studies have been executed using measures of these global dispositional constructs from the contemporary field of personality. This study explored whether the Big Five personality factors (Extraversion, Neuroticism, Agreeableness, Conscientiousness, and Intellect) were concurrently associated with key smoking (e.g., nicotine dependence, smoking rate, age at first cigarette) and cessation (e.g., self-efficacy to quit, motivation to quit, number of prior quit attempts, length of most recent quit) variables in a sample of regular smokers (n = 130). Of the 35 correlations computed, only 2 were significant: Intellect was positively correlated with motivation to quit and number of 24-hr quit attempts in the last year. These results have implications for using trait variables to study individual differences in smokers.

The Relation of Psychopathic Characteristics and Anxiety in Noncriminals: Physiological and Cognitive Responses to Guided Imagery

Abstract: In response to a paucity of research examining the phenomenology of psychopathy among nonforensic samples, the present study explored the relations among psychopathic traits, self-reported anxiety, and physiological reactivity to experimental stimuli. Undergraduate students with no history of criminal behavior listened to four audiotaped vignettes designed to elicit affective responses. Imagery and anxiety ratings, as well as physiological indices supported the utility of the experimental manipulation. Consistent with data obtained among forensic samples, participants with greater psychopathic characteristics exhibited electrodermal hyporeactivity in response to guided imagery. However, inconsistent with previous findings, hyporeactivity was primarily related to high emotional detachment rather than elevated levels of deviant behavior. Results also suggested certain psychopathic qualities (emotional detachment) may be more associated with somatic and trait anxiety than other characteristics (deviant behavior), although anxiety did not moderate the effects of psychopathic characteristics on physiological responding. Theoretical implications are addressed, including the possible generalizability of psychophysiological models of diagnosed psychopaths to individuals with more benign psychopathic characteristics.

The Differential Assessment of State-Trait Anxiety and Depression in a Clinically Anxious Sample

Abstract: Empirical investigation into anxiety and depression has led some researchers to question the conceptual distinctness of these constructs. N. S. Endler, B. J. Cox, J. D. A. Parker, and R. M. Bagby (1992) provided empirical evidence that state and trait anxiety (using the Endler Multidimensional Anxiety Scales; N. S. Endler, J. M. Edwards, and R. Vitelli, 1991) may be differentiated from depression (using the Beck Depression Inventory; A. T. Beck, 1978) in a student sample. The present study extended this research by employing a different sample, a clinical sample of panic disorder patients (N = 189). Further support for the conceptual distinctness of anxiety and depression is presented herein. The concept of a general distress factor that encompasses both constructs is also discussed.

Trends in Anxiety Assessment

Abstract: Trends in anxiety assessment were established by examining the methods reported in anxiety-related papers published in three prominent behavior therapy journals from 1970 to 2002. Assessment methods were categorized using Lang's three-system concept of anxiety (P. J. Lang, 1968) as an organizational framework. Analysis of the research methods suggests two primary patterns. First, multisystem assessment declined in the last several years by comparison with previous years whereas the assessment of a single response system (typically self-report) has increased. Second, among anxiety-related papers reporting multimodal assessment, physiological assessment returned to 1970s-era frequency in recent years after an upsurge in the mid-1980s and early 1990s. Some possible interpretations and implications of these trends are discussed.

Debiasing of Pessimistic Judgments Associated with Anxiety

Abstract: This study tested the Consider-An-Alternative debiasing procedure and its ability to reduce pessimistic judgmental predictions associated with anxiety. Study participants were randomly assigned to either a control group or a debiasing group and were asked to rate the likelihood of hypothetical events. Level of trait anxiety was assessed to assign participants to a “normal” and a highly anxious group. The results showed that the debiasing procedure was effective in the reduction of pessimistic judgmental predictions for participants with both high and “normal” levels of trait anxiety. Specifically, the generation of alternative positive information significantly reduced pessimistic predictions of future events. The results were discussed in terms of availability of information in memory and cognitive biases.

Behavior Ratings and Observations of Externalizing Symptoms in Girls: The Role of Child Popularity with Adults

Abstract: This study examined staff ratings and live observations of externalizing behavior in 149 girls with and without attention-deficit/hyperactivity disorder (ADHD), who participated in all-female naturalistic research camps. Girls' popularity with adult camp staff was hypothesized to explain discrepancies between ratings and observations. Compared to behavior observations, staff ratings overestimated the externalizing behavior of girls who were disliked by staff. In contrast, ratings and observations were consistent for girls who were liked by staff. Among girls who were disliked by staff, unpopularity with peers predicted a larger discrepancy between staff ratings and observations, but peer status made little difference in rating–observation discrepancies of girls liked by staff. All results held after controlling for the participants' ADHD versus comparison status. Results suggest that staff ratings may be biased by personal feelings about children and that direct observations may be more immune to such bias.

The use of the MMPI-2 infrequency-psychopathology scale in the assessment of posttraumatic stress disorder in male veterans.

Abstract: This study evaluated the use of the FP (Infrequency–Psychopathology) scale of the Minnesota Multiphasic Personality Inventory—2 (MMPI-2) as a measure of symptom overreporting among 423 service-seeking male veterans with and without PTSD. Results were consistent with several predictions based on the logic of the FP scale. FP produced lower scores for PTSD and non-PTSD patients than the other two MMPI-2 measures of infrequent responding; F and FB. FP also resulted in fewer invalid protocols than did F or FB. Finally, FP yielded lower correlations with MMPI-2 and other measures of psychopathology than did F or FB. Consistent with previous studies, compensation-seeking status was associated with extreme elevations across clinical and validity scales. Contrary to previous findings, however, compensation-seeking veterans were also more likely to receive a PTSD diagnosis. Implications for the relationship between compensation seeking and symptom overreporting are discussed.

Neurobehavioral correlates of chronic hepatitis C

Abstract: Chronic infection with the hepatitis C virus is a major public health concern in the United States and worldwide, and persons with psychiatric histories are more likely to have chronic hepatitis C (CHC) Neurobehavioral consequences of CHC are common in all phases of the disease process and significantly contribute to morbidity Antiviral treatment also is associated with neurobehavioral difficulties that can interfere with successful completion of treatment and result in fewer patients clearing the virus Fatigue, depression, cognitive dysfunction, and anxiety are the most common neuropsychiatric symptoms reported by patients with CHC regardless of treatment status Behavioral health care professionals can play a vital role in decreasing the personal and societal burden of CHC by being active members of the treatment team and by furthering knowledge of how to manage neurobehavioral correlates of CHC

Relationships Between Treatment Components, Client-Level Factors, and Positive Treatment Outcomes

Abstract: How different amounts and components of treatment affect substance abuse treatment outcomes is fundamentally important to evaluating current treatment practices and recommending improvements. Through a secondary analysis of data from the National Treatment Improvement Evaluation Study (NTIES), the present study examined the relationships between treatment components, client-level factors, and positive treatment outcomes. Several components were shown tohave significant effects on the odds of a positive outcome, over and above the effects of client background characteristics. Depending on treatment modality, these included length of stay; whether or not clients reported seeing their treatment plan hours per month in group and individual counseling; utilization ofeducational, vocational, and other ancillary services; use of antianxiety and drug and alcohol medications; and client matching. Several interactions between client-level factors and treatment components were also observed. Studylimitations are discussed, followed by implications for policy and practiceand suggestions for further research.