https://cronfa.swan.ac.uk/Record/cronfa36004/Download/0036004-07112017134327.pdf

The effects of improving sleep on mental health (OASIS): a randomised controlled trial with mediation analysis

Community-based studies suggest that cannabis products that are high in Δ⁹-tetrahydrocannabinol (THC) but low in cannabidiol (CBD) are particularly hazardous for mental health. Laboratory-based studies are ideal for clarifying this issue because THC and CBD can be administered in pure form, under controlled conditions. In a between-subjects design, we tested the hypothesis that pre-treatment with CBD inhibited THC-elicited psychosis and cognitive impairment. Healthy participants were randomised to receive oral CBD 600 mg (n=22) or placebo (n=26), 210 min ahead of intravenous (IV) THC (1.5 mg). Post-THC, there were lower PANSS positive scores in the CBD group, but this did not reach statistical significance. However, clinically significant positive psychotic symptoms (defined a priori as increases ≥ 3 points) were less likely in the CBD group compared with the placebo group, odds ratio (OR)=0.22 (χ²=4.74, p<0.05). In agreement, post-THC paranoia, as rated with the State Social Paranoia Scale (SSPS), was less in the CBD group compared with the placebo group (t=2.28, p<0.05). Episodic memory, indexed by scores on the Hopkins Verbal Learning Task-revised (HVLT-R), was poorer, relative to baseline, in the placebo pre-treated group (-10.6 ± 18.9%) compared with the CBD group (-0.4% ± 9.7 %) (t=2.39, p<0.05). These findings support the idea that high-THC/low-CBD cannabis products are associated with increased risks for mental health.

Cannabidiol inhibits THC-elicited paranoid symptoms and hippocampal-dependent memory impairment

Background Judging whether we can trust other people is central to social interaction, despite being error-prone. A fear of others can be instilled by the contemporary political and social climate. Unfounded mistrust is called paranoia, and in severe forms is a central symptom of schizophrenia. Aims To demonstrate that individuals without severe mental illness in the general population experience unfounded paranoid thoughts, and to determine factors predictive of paranoia using the first laboratory method of capturing the experience. Method Two hundred members of the general public were comprehensively assessed, and then entered a virtual reality train ride populated by neutral characters. Ordinal logistic regressions (controlling for age, gender, ethnicity, education, intellectual functioning, socio-economic status, train use, playing of computer games) were used to determine predictors of paranoia. Results The majority agreed that the characters were neutral, or even thought they were friendly. However, a substantial minority reported paranoid concerns. Paranoia was strongly predicted by anxiety, worry, perceptual anomalies and cognitive inflexibility. Conclusions This is the most unambiguous demonstration of paranoid ideation in the general public so far. Paranoia can be understood in terms of cognitive factors. The use of virtual reality should lead to rapid advances in the understanding of paranoia.

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Virtual reality study of paranoid thinking in the general population.

https://www.thelancet.com/pdfs/journals/lanpsy/PIIS2215-0366(15)00039-5.pdf

Effects of cognitive behaviour therapy for worry on persecutory delusions in patients with psychosis (WIT): a parallel, single-blind, randomised controlled trial with a mediation analysis

A social factor that has gained recent attention in understanding psychosis is trauma. In the current study the association of a history of trauma with persecutory ideation and verbal hallucinations was tested in the general public. Further, putative mediation variables including anxiety, depression and illicit drug use were examined. In a cross-sectional study, 200 members of the UK general public completed self-report questionnaires. A history of trauma was significantly associated with both persecutory ideation and hallucinations. Severe childhood sexual abuse and non-victimisation events were particularly associated with psychotic-like experiences. The association of trauma and paranoia was explained by levels of anxiety. The association of trauma and hallucinations was not explained by the mediational variables. The study indicates that trauma may impact non-specifically on delusions via affect but that adverse events may work via a different route in the occurrence of hallucinatory experience. These ideas require tests in longitudinal designs.

Routes to psychotic symptoms: trauma, anxiety and psychosis-like experiences.

BackgroundParanoia is increasingly being studied in clinical and non-clinical populations. However there is no multi-dimensional measure of persecutory ideas developed for use across the general population-psychopathology continuum. This paper reports the development of such a questionnaire: the ‘Green et al. Paranoid Thought Scales’. The aim was to devise a tool to assess ideas of persecution and social reference in a simple self-report format, guided by a current definition of persecutory ideation, and incorporating assessment of conviction, preoccupation and distress.MethodA total of 353 individuals without a history of mental illness, and 50 individuals with current persecutory delusions completed a pool of paranoid items and additional measures to assess validity. Items were devised from a recent definition of persecutory delusions, current assessments of paranoia, the authors' clinical experience, and incorporated dimensions of conviction, preoccupation and distress. Test–retest reliability in the non-clinical group was assessed at 2 weeks follow-up, and clinical change in the deluded group at 6 months follow-up.ResultsTwo 16-item scales were extracted, assessing ideas of social reference and persecution. Good internal consistency and validity was established for both scales and their dimensions. The scales were sensitive to clinical change. A hierarchical relationship between social reference and persecution was found. The data provide further evidence for a continuum of paranoid ideas between deluded and healthy individuals.ConclusionsA reliable and valid tool for assessing paranoid thoughts is presented. It will provide an effective way for researchers to ensure consistency in research and for clinicians to assess change with treatment.

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/4FDC2275DF3AE6D44BF86C60AEF84CE5/S0033291707001638a.pdf/div-class-title-measuring-ideas-of-persecution-and-social-reference-the-green-span-class-italic-et-al-span-paranoid-thought-scales-gpts-div.pdf

Cel Green

Papers

Measuring ideas of persecution and social reference: the Green et al. Paranoid Thought Scales (GPTS)