Daniel Varghese

Association between cannabis use and psychosis-related outcomes using sibling pair analysis in a cohort of young adults.

CONTEXT Prospective cohort studies have identified an association between cannabis use and later psychosis-related outcomes, but concerns remain about unmeasured confounding variables. The use of sibling pair analysis reduces the influence of unmeasured residual confounding. OBJECTIVE To explore the association between cannabis use and psychosis-related outcomes. DESIGN A sibling pair analysis nested within a prospective birth cohort. SETTING Births at a Brisbane, Australia, hospital. PARTICIPANTS Three thousand eight hundred one young adults born between 1981 and 1984 as part of the Mater-University Study of Pregnancy. MAIN OUTCOME MEASURES Cannabis use and 3 psychosis-related outcomes (nonaffective psychosis, hallucinations, and Peters et al Delusions Inventory score) were assessed at the 21-year follow-up. Associations between duration since first cannabis use and psychosis-related outcomes were examined using logistic regression adjusted for sex, age, parental mental illness, and hallucinations at the 14-year follow-up. Within 228 sibling pairs, the association between within-pair differences in duration since first cannabis use and Peters et al Delusions Inventory score was examined with general linear modeling. The potential impact of attrition was examined. RESULTS Duration since first cannabis use was associated with all 3 psychosis-related outcomes. For those with duration since first cannabis use of 6 or more years, there was a significantly increased risk of (1) nonaffective psychosis (adjusted odds ratio, 2.2; 95% confidence interval, 1.1-4.5), (2) being in the highest quartile of Peters et al Delusions Inventory score (adjusted odds ratio, 4.2; 95% confidence interval, 4.2-5.8), and (3) hallucinations (adjusted odds ratio, 2.8; 95% confidence interval, 1.9-4.1). Within sibling pairs, duration since first cannabis use and higher scores on the Peters et al Delusions Inventory remained significantly associated. CONCLUSIONS Early cannabis use is associated with psychosis-related outcomes in young adults. The use of sibling pairs reduces the likelihood that unmeasured confounding explains these findings. This study provides further support for the hypothesis that early cannabis use is a risk-modifying factor for psychosis-related outcomes in young adults.

The association between delusional-like experiences and suicidal thoughts and behaviour

BACKGROUND Delusional-like experiences (DLEs) are common in the general population. Whilst it is well known that psychotic disorders increase the risk of suicide, it is unclear if DLEs are also associated with suicidal thoughts and behaviour. This study aims to explore these variables in a large population-based sample. METHOD Participants were drawn from a national survey of mental health (n=8841) in Australia. The Composite International Diagnostic Interview was used to identify DLEs, psychiatric disorders, and information related to suicidal ideation, suicide plan and suicide attempts. We examined the relationship between DLEs and suicidal ideation, plans and attempts using logistic regression, adjusted for a range of potentially confounding variables. RESULTS 8.4% of subjects endorsed one or more DLEs. 12.9% subjects reported suicidal ideation, 3.8% suicidal plans, and 3.0% a suicide attempt at some point in their lives. Those with any DLE were about two to four times as likely to report suicidal ideation, plans or attempts. There was a dose response relationship between DLEs and endorsement of suicide-related items. CONCLUSIONS DLEs are common in the general population and appear to be independently associated with suicidal thoughts and behaviour. DLE may provide a marker of vulnerability to suicide, and thus could be of value in future suicide prevention research.

The association between general psychological distress and delusional-like experiences: a large population-based study.

BACKGROUND Delusional-like experiences (DLE) are prevalent in the community, and are associated with the both clinical and subclinical depression and anxiety. The aim of this study was to explore the association between general psychological distress and DLE adjusting for the presence of psychiatric disorders in a large population-based sample. METHODS Subjects were drawn from the Australian National Survey of Mental Health and Wellbeing 2007 (n=8841). DLE were assessed using a modified World Mental Health Composite International Diagnostic Interview (CIDI) schedule, and psychological distress was measured using the Kessler-10 (K10) short questionnaire. We examined the relationship between DLE and quartiles of K10 scores using logistic regression, adjusting for depression and anxiety disorders, and other potential confounding factors. The analyses were also repeated in the subgroup of the sample who were free of lifetime clinical diagnoses. RESULTS Of the participants, 776 (8.4%) endorsed one or more DLE. Individuals with moderate and severe psychological distress were two to three times more likely to endorse DLE. The association remained significant after adjusting for potential confounding factors, and in the subgroup of the population who remained after excluding those who met criteria for lifetime diagnosis for any mental disorder. CONCLUSION While DLE have traditionally been associated with psychotic disorders, our results suggest that they are associated with non-specific psychological distress in otherwise-well individuals.

The association between delusional-like experiences, and tobacco, alcohol or cannabis use: a nationwide population-based survey

BackgroundPrevious population-based studies have found that delusional-like experiences (DLE) are prevalent in the community, and are associated with a wide range of mental health disorders including substance use. The aim of the study was to explore the association between DLE and three commonly used substances - tobacco, alcohol and cannabis.MethodsSubjects were drawn from the Australian National Survey of Mental Health and Wellbeing 2007. The Composite International Diagnostic Interview was used to identify DLE, common psychiatric disorders, and substance use. We examined the relationship between the variables of interest using logistic regression, adjusting for potential confounding factors.ResultsOf 8 773 participants, 8.4% (n = 776) subjects endorsed one or more DLE. With respect to tobacco use, compared to nonusers, DLE were more common in those who (a) had daily use, (b) commenced usage aged 15 years or less, and (c) those who smoked heavily (23 or more cigarettes per day). Participants with cannabis use disorders were more likely to endorse DLE; this association was most prominent in those with an onset of 16 years or younger. In contrast, the pattern of association between DLE versus alcohol use or dependence was less consistent, however those with early onset alcohol use disorders were more likely to endorse DLE probe items.ConclusionsWhile cannabis use disorders have been previously linked with DLE, our findings linking alcohol and tobacco use and DLE suggest that the influence of these substances on psychosis-related outcomes warrants closer scrutiny in longitudinal prospective studies.

Correlates of delusion-like experiences in a non-psychotic community sample.

Objective: Several large population-based studies have reported that otherwise-well individuals endorse items related to delusion-like experiences. The aim of the present study was to examine selected correlates of delusion-like experiences in a sample of non-psychotic individuals. Method: Subjects (n=310) were screened with the Diagnostic Interview for Psychosis in order to exclude psychotic disorders. Delusion-like experiences were assessed with the Peters Delusional Inventory (PDI). Non-parametric statistics were used to assess the relationship between total PDI score and a range of demographic (age, sex, migrant status, paternal age), physical (minor physical anomalies) symptom-related variables (hallucinations, awareness of thought disorder) and family history of mental illness. Results: The median (range) PDI score was 4 (0–26), while one-third of the subjects endorsed seven or more items. The presence of a family history of any psychiatric condition was significantly correlated with a higher PDI score. PDI score was significantly positively correlated with endorsement of hallucinations and awareness of thought disorder. PDI was not significantly associated with sex, family history of schizophrenia, paternal age, migrant status nor scores related to minor physical anomalies. There was a trend level association between younger age and higher PDI score. Conclusion: Delusion-like experiences are relatively common in non-psychotic individuals. The association with a family history of mental disorders provides clues to the mechanisms underlying the profile of delusion-like experience.

The association between trauma and delusional-like experiences.

Individuals exposed to childhood trauma are more likely to report delusional-like experiences (DLE). This study examined the association between trauma exposure and DLE in a large community sample, investigating different trauma types and age-at-first-exposure to trauma. Subjects were from the Australian National Survey of Mental Health and Wellbeing 2007. Associations between DLE and (i) exposure to different trauma types and (ii) age-at-first-exposure were assessed using logistic regression with adjustments for potential confounding factors. 8.4% of 8773 subjects reported DLE and almost 75% reported at least one traumatic event. Exposure to a traumatic event was significantly associated with more than twice the odds of delusional-like experiences and exposure to more types of trauma increased the likelihood of DLE in a dose dependent fashion. The majority of the individual trauma items were independently associated with any endorsement of DLE. First exposure of trauma in childhood, adolescence and adulthood was all associated with DLE. Further understanding of biological and cognitive pathways is required to unravel the association between trauma exposure and delusional-like experiences.

Anxiety and depressive disorders are associated with delusional-like experiences: a replication study based on a National Survey of Mental Health and Wellbeing

Objectives There is growing evidence that delusional-like experiences (DLE) are associated with common mental disorders. In particular, a National Mental Health Survey conducted in Australia during 2007 reported an association between DLE and both anxiety disorder and major depressive disorder (MDD). However, the previous study did not examine this association with respect to subtypes of anxiety disorder nor with severity of MDD. The aim of this study was to examine the associations between DLE and both anxiety disorder and MDD in more detail based on an independent population sample. Design Cross-sectional study. Setting Subjects were drawn from the Australian Survey of Mental Health and Wellbeing 1997 using a stratified multistage area sampling of persons living in private dwellings in all States and Territories of Australia. Participants Approximately 13 600 private dwellings were initially selected with one person aged 18 years or older from each dwelling invited to participate. In total, 10 641 individuals participated in the survey. Primary and secondary outcome measures The Composite International Diagnostic Interview was used to identify individuals with DLE and Diagnostic and Statistical Manual of Mental Disorder, Fourth Edition (DSM IV) lifetime diagnoses of anxiety disorders and MDD. The influence of various anxiety disorders and MDD on DLE was assessed with logistic regression. Results Having a lifetime diagnosis of either any anxiety disorder or MDD was significantly associated with the endorsement of DLE. The association was found for each of the main anxiety disorders when examined separately. There was a dose–response relationship between increasing severity of MDD and higher odds of DLE endorsement. Conclusions DLE are associated with a wide range of anxiety disorders and are more prevalent in those with MDD. Understanding the relationship between DLE, anxiety disorders and depression may provide insights into shared pathways that underpin both psychotic disorders and common mental disorders.

The Association between Physical Health and Delusional-Like Experiences: A General Population Study

Objective Delusional-like experiences (DLE) are prevalent in the community. Recent community based studies have found that DLE are more common in those with depression and anxiety disorders, and in those with subclinical symptoms of depression and anxiety. Chronic physical disorders are associated with comorbid depression and anxiety; however, there is a lack of evidence about the association of DLE with common physical conditions. The aim of this study was to explore associations between the common physical disorders and DLE using a large population sample. Methods Subjects were drawn from the Australian National Survey of Mental Health and Wellbeing 2007, a national household survey of 8841 residents aged between 16 and 85 years. The presence of DLE, selected common physical disorders and symptoms were assessed using a modified World Mental Health Composite International Diagnostic Interview (CIDI) schedule. We examined the relationship between DLE, and physical health-related variables using logistic regression, with adjustments for potential confounding factors. Results Of the 8771, 776 (8.4%) subjects positively endorsed one or more DLE. Of the six physical disorders examined, only diabetes and arthritis were significantly associated with the endorsement of DLE. Of the seven broad physical symptoms explored, only hearing problems were consistently associated with DLE. Conclusion Delusional-like experiences are common in the Australian community, and are associated with selected chronic physical disorders and with impaired hearing. The direction of causality between these variables warrants closer research scrutiny.

Social support and delusional-like experiences: a nationwide population-based study

BACKGROUND Population-based studies have identified that delusional-like experiences (DLEs) are common in the general population. While there is a large literature exploring the relationship between poor social support and risk of mental illness, there is a lack of empirical data examining the association of poor social support and DLEs. The aim of the study was to explore the association between social support and DLEs using a large, nationally representative community sample. METHODS Subjects were drawn from a national multistage probability survey of 8841 adults aged between 16 and 85 years. The Composite International Diagnostic Interview was used to identify DLEs, common psychiatric disorders and physical disorders. Eight questions assessed various aspects of social support with spouse/partners and other family and friends. We examined the relationship between DLEs and social support using logistic regression, adjusting for potential confounding factors. RESULTS Of the sample, 8.4% (n = 776) positively endorsed one or more DLEs. Individuals who (a) had the least contact with friends, or (b) could not rely on or confide in spouse/partner, family or friends were significantly more likely to endorse DLEs. The associations remained significant after adjusting for a range of potential confounding factors. CONCLUSIONS DLEs are associated with impoverished social support in the general population. While we cannot exclude the possibility that the presence of isolated DLEs results in a reduction of social support, we speculate that poor social support may contribute in a causal fashion to the risk of DLEs.

Socio-economic disadvantage and delusional-like experiences: A nationwide population-based study

PURPOSE Delusional-like experiences (DLE) have been associated with low income, suggesting that more broadly defined socio-economic disadvantage may be associated with these experiences. We had the opportunity to explore the association between DLE and both individual- and area-level measures of socio-economic disadvantage. METHOD Subjects were drawn from the Australian National Survey of Mental Health and Wellbeing 2007. The Composite International Diagnostic Interview was used to identify DLE, common psychiatric disorders, and physical disorders. Individual-level and area-level socio-economic disadvantage measures were available based on variables including income, educational attainment, employment status, and housing. We examined the relationship between the variables of interest using logistic regression, adjusting for potential confounding factors. RESULTS Of the 8773 subjects, 8.4% (n=776) positively endorsed one or more DLE. DLE screen items were more likely to be endorsed by those who were (a) younger, (b) never married, or widowed, separated or divorced status, (c) migrants, or (d) living in rented houses. There were significant associations between socio-economic disadvantage and increased DLE endorsement, and this was found for both individual-level and area-level measures of socio-economic disadvantage. In general, the associations remained significant after adjusting for a range of potential confounding factors and in planned sensitivity analyses. CONCLUSIONS DLE are associated with socio-economic disadvantage in the general population. We speculate that the link between socio-economic disadvantage and DLE may be mediated by psychosocial stress and general psychological distress.