Cannabis use and non‐clinical dimensions of psychosis in university students presenting to primary care

Skinner R, Conlon L, Gibbons D, McDonald C. Cannabis use and non‐clinical dimensions of psychosis in university students presenting to primary care. Objective: To explore the relationship between cannabis use and self‐reported dimensions of psychosis in a population of university students presenting for any reason to primary care. Method: One thousand and forty‐nine students attending the Student Health Unit, National University of Ireland, Galway, completed self‐report questionnaires on alcohol and substance misuse, non‐clinical dimensions of psychosis [Community Assessment of Psychic Experiences (CAPE)], anxiety and depression [Hospital Anxiety and Depression Scale (HADS)]. Association of cannabis use with psychiatric symptoms was explored whilst controlling for confounds. Results: More frequent cannabis use was independently associated with greater intensity of positive, negative and depressive psychotic symptoms. The earlier the age of onset of cannabis use, the more positive psychotic symptoms were reported. Conclusion: These findings support the hypotheses that cannabis use increases the risk of developing psychotic symptoms and that this risk is further increased in those individuals who use cannabis more heavily and commence it at a younger age.     

Sex differences in symptoms of psychosis in a non-selected,general population sample

BACKGROUND: Little is known about sex differences in psychosis beyond the borders of clinical disorder. METHODS: A general population sample of 7,076 subjects was assessed using the Composite International Diagnostic Interview, in order to explore sex differences in the prevalence of any positive and negative symptoms of psychosis, and to examine to what degree any differences could be explained by differences in level of affective symptoms. RESULTS: Male sex was associated with higher prevalence of negative symptoms (OR = 1.6, 95% CI = 1.0, 2.5), independent of differences in affective symptoms and presence of DSM-III-R psychotic disorder. Women had higher rates of positive psychotic experiences (OR = 0.8, 95% CI = 0.7, 0.9), but this difference disappeared after adjustment for depressive symptoms (adjusted OR = 1.2, 95% CI = 0.9, 1.5). CONCLUSION: The sex differences in psychopathology that are seen in schizophrenia are expressed beyond the clinical phenotype, suggesting sex-dependent continuous and normal variation of several psychosis dimensions. The higher rates of positive psychotic experiences seen in women may be secondary to differences in the rate of affective symptoms.     

How psychotic are individuals with non-psychotic disorders?

BACKGROUND: The objective of this study was to compare, using a self-report questionnaire, the dimensions of psychosis across different patient groups in a community mental health service (CMHS) and in non-patients in the general population. METHODS: The Community Assessment of Psychic Experiences (CAPE) is a 40-item self-report instrument with positive, negative and depressive symptom dimensions. Seven hundred and sixty-two patients and 647 subjects in the general population filled in the CAPE. In 555 of the 762 patients, a DSM-IV diagnosis was made. The following DSM-IV categories were used in the analyses: 1. Schizophrenia and Other Psychotic Disorders (n = 72), 2. Mood Disorders (n = 214), 3. Anxiety Disorders (n = 129). The patient and non-patient groups were compared on the three dimensions of the CAPE using multivariate regression analysis. RESULTS: The patient groups scored significantly higher on the positive, negative and depressive dimensions than the non-patients. Patients with psychotic disorders had the greatest difference in positive psychosis items compared to non-patients (beta = 0.94, 95 % CI: 0.7-1.18), whereas patients with mood and anxiety disorders had the highest depressive symptom scores, and positive symptom scores that were intermediate to that of non-patients and patients with psychotic disorders (mood disorders: beta = 0.53, 95 % CI: 0.39-0.68; anxiety disorders: beta = 0.22, 95 % CI: 0.04-0.39). The CAPE distress score adjusted for the corresponding frequency score was not significantly different between the patient groups, but compared to the general population, patient status did contribute significantly to the level of distress. DISCUSSION: Patients with anxiety and mood disorders had elevated scores on positive psychosis items, indicating that expression of psychosis in non-psychotic disorders is common. The finding of elevated scores of the patient groups on all three dimensions compared to non-patients suggests that the psychopathology associated with psychotic disorders varies quantitatively across DSM-IV categories.     

Cannabis use and outcome of recent onset psychosis.

PURPOSE: To test the hypothesis that recent onset psychotic patients who use cannabis will have psychotic symptoms that are more severe and more persistent than those who do not use cannabis. SUBJECTS AND METHODS: We carried out a 4-year follow-up study of a cohort of 119 patients with recent onset of psychosis. The patients were divided into four groups according to duration of cannabis use, taking index admission and follow-up as reference points. RESULTS: Those subjects who persisted in the use of cannabis had more positive (but not negative) symptoms and a more continuous illness at follow-up. LIMITATIONS: The main limitations of the study were: the relatively small sample size, and that the excess of male subjects and the presence of cannabis induced psychosis could have a confusing impact on the interpretation of the results. CONCLUSION: It is possible that psychotic patients who use cannabis are at a greater risk of a more continuous illness with more positive symptoms than those who do not.     

Self-reported psychosis-like symptoms and the continuum of psychosis

Background: It has been suggested that psychotic symptoms may be distributed along a continuum that extends from normality through depressive states to schizophrenia with increasing level of severity. This study examined the hypothesis that the severity of positive psychotic symptoms increases from normality, through depression/anxiety states to clinical psychosis. Methods: Consecutive general practice attenders completed a self-report questionnaire of 24 items of delusional ideation and hallucinatory experiences and the GHQ-12. The following groups were compared: (1) subjects with a diagnosis of psychosis (n = 57), (2) GHQ cases (n = 245), and (3) GHQ non-cases (n = 378). Results: Quantitative differences were apparent in the great majority of items on delusional ideation and hallucinatory experiences, in that normals scored lowest, psychosis patients scored highest and GHQ cases scored in between. This pattern of differences was apparent for all dimensions of psychosis-like experiences, including the more “schizophrenic” ones, with the exception of Grandiosity (GHQ cases similar to normals) and Paranormal Beliefs (no differences between the three groups). Conclusions: Similar to findings in aetiological research, phenotypic differences between normal controls, patients with anxiety/depression and patients with psychosis appear quantitative rather than qualitative for core dimensions of psychosis. Accepted: 15 June 1999     

Testing the psychosis continuum: differential impact of genetic and nongenetic risk factors and comorbid psychopathology across the entire spectrum of psychosis

A growing number of studies demonstrate high rates of subthreshold psychotic experiences, but there is considerable heterogeneity in rates due to study cohort and design factors, obscuring how prevalent psychotic experiences may or may not relate to rare psychotic disorders. In a representative general population sample (n = 4011) in Izmir, Turkey, the full spectrum of expression of psychosis was categorized across 5 groups representing (1) absence of psychosis, (2) subclinical psychotic experiences, (3) low-impact psychotic symptoms, (4) high-impact psychotic symptoms, and (5) full-blown clinical psychotic disorder and analyzed for continuity and discontinuity in relation to (1) other symptom dimensions associated with psychotic disorder and (2) proxies of genetic and nongenetic etiology. Results were tested for linear and extralinear contrasts between clinical and nonclinical and between disorder and nondisorder expression of psychosis. Demographic variables, indexing premorbid social adjustment and socioeconomic status, impacted mostly linearly; proxy variables of genetic loading (more or more severely affected relatives) impacted in a positive extralinear fashion; environmental risk factors sometimes impacted linearly (urbanicity and childhood adversity) and sometimes extralinearly (cannabis), occasioning a disproportional shift in risk at the clinical disorder end of the spectrum. Affective symptoms were associated with a disproportionally higher risk below the disorder threshold, whereas a disproportionally higher risk above the threshold was associated with psychotic symptom load, negative symptoms, disorganization, and visible signs of mental illness. Liability associated with respectively affective and nonaffective symptom domains, in interaction with environmental risks, may operate by impacting differentially over a quasi-continuous extended psychosis phenotype in the population.     

Psychosis risk as a function of age at onset

BACKGROUND: Little is known about late-onset psychosis (onset after the age 45 years) and how it relates to early-onset psychosis (before age 45 years). The aims of this study were to calculate the incidence of non-affective, non-organic psychotic symptoms across the life span and to explore the contribution of different sets of risk factors in relation to age at onset. METHODS: Data were obtained from the three measurements of the Netherlands Mental Health Survey and Incidence Study. Symptoms of psychosis were assessed in individuals aged 18-64 years using the Composite International Diagnostic Interview. All individuals reporting first-onset of psychotic symptoms within a three-year interval were included. The degree to which sets of risk factors affected the psychosis outcome similarly across age groups was assessed. RESULTS: The number of subjects displaying incident psychotic symptoms was similar across age groups. Cumulative incidence rates ranged from 0.3% to 0.4%. Age differences were found for life-time depressive symptoms (risk difference = 5%, 95% CI = 1%, 9%) and baseline neuroticism (risk difference = 3%, 95% CI = 0%, 6%), indicating that late-onset psychosis was less often preceded by these. In contrast, no effect modification by age was observed for female sex, hearing impairment, being single, or life-time cannabis use. CONCLUSIONS: Onset of psychotic symptoms in late life is no rare event. Compared to early onset psychosis, the late-onset counterpart less often arises in a context of emotional dysfunction and negative affectivity, suggesting qualitative differences in aetiology and more effective premorbid coping styles.     

Agreement between self-rated and clinically assessed symptoms in subjects with psychosis

The aim of this study was to explore the capacity of acutely ill patients with psychosis (N = 40) to self-report their symptoms by comparing self-assessment and objective measures. Positive, negative, and depressive symptoms were rated using the Scale for the Assessment of Positive Symptoms, the Scale for the Assessment of Negative Symptoms, and the Calgary Depression Scale. Insight level was measured using the Scale to Assess Unawareness of Mental Disorder. Patients were asked to self-report positive, negative, and depressive symptoms using the Community Assessment of Psychic Experience. Patients presenting with acute psychotic disorders are able to assess fairly their positive, negative, and depressive symptoms. Significant associations were found between self-reported and objective measures of positive, negative, and depressive symptoms independently of insight level. Individual positive and negative symptoms were correctly self-assessed, except for persecutory delusion and alogia, respectively. These results suggest that self-report questionnaires can be used in educational programs to favor the patient's therapeutic adherence.     

The Impact of Cannabis Use on Clinical Outcomes in Recent Onset Psychosis

Background: There are inconsistencies in findings as to whether cannabis use has a negative impact on clinical outcomes for people with established psychosis. Effects may be more evident on patients with recent onset psychosis. Aim: To investigate the relationship between cannabis use and clinical outcome, including whether change in cannabis use affects psychotic symptoms, affective symptoms, functioning and psychotic relapse in a sample of people in early psychosis with comorbid cannabis abuse or dependence. Methods: One hundred and ten participants were examined prospectively with repeated measures of substance use antecedent to psychopathology at baseline, 4.5, 9, and 18 months. We used random intercept models to estimate the effects of cannabis dose on subsequent clinical outcomes and whether change in cannabis use was associated with change in outcomes. Results: There was no evidence of a specific association between cannabis use and positive symptoms, or negative symptoms, relapse or hospital admissions. However, a greater dose of cannabis was associated with subsequent higher depression and anxiety. Change in the amount of cannabis used was associated with statistically significant corresponding change in anxiety scores, but not depression. Additionally, reductions in cannabis exposure were related to improved patient functioning. Conclusions: Reducing cannabis may be directly associated with improvements in anxiety and functioning, but not other specific symptoms.Key words: psychosis, cannabis, substance use, dual diagnosis     

Cannabinoids and psychosis

Recent advances in knowledge about cannabinoid receptor function have renewed interest in the association between cannabis and psychosis. Case series, autobiographical accounts, and surveys of cannabis users in the general population suggest an association between cannabis and psychosis. Cross-sectional studies document an association between cannabis use and psychotic symptoms, and longitudinal studies suggest that early exposure to cannabis confers a close to two-fold increase in the risk of developing schizophrenia. Pharmacological studies show that cannabinoids can induce a full range of transient positive, negative, and cognitive symptoms in healthy individuals that are similar to those seen in schizophrenia. There is considerable evidence that in individuals with an established psychotic disorder such as schizophrenia, exposure to cannabis can exacerbate symptoms, trigger relapse, and worsen the course of the illness. Only a very small proportion of the general population exposed to cannabis develop a psychotic illness. It is likely that cannabis exposure is a ‘component cause’ that interacts with other factors to ‘cause’ schizophrenia or other psychotic disorder, but is neither necessary nor sufficient to do so alone. Further work is necessary to identify the factors that underlie individual vulnerability to cannabinoid-related psychosis and to elucidate the biological mechanisms underlying this risk.     

The Independent Effects of Psychosocial Stressors on Subclinical Psychosis: Findings From the Multinational EU-GEI Study

The influence of psychosocial stressors on psychosis risk has usually been studied in isolation and after the onset of the disorder, potentially ignoring important confounding relationships or the fact that some stressors that may be the consequence of the disorder rather than preexisting. The study of subclinical psychosis could help to address some of these issues. In this study, we investigated whether there was (i) an association between dimensions of subclinical psychosis and several psychosocial stressors including: childhood trauma, self-reported discrimination experiences, low social capital, and stressful life experiences, and (ii) any evidence of environment–environment (ExE) interactions between these factors. Data were drawn from the EUGEI study, in which healthy controls (N = 1497) and siblings of subjects with a psychotic disorder (N = 265) were included in six countries. The association between psychosocial stressors and subclinical psychosis dimensions (positive, negative and depressive dimension as measured by the Community Assessment of Psychic Experiences (CAPE) scale) and possible ExE interactions were assessed using linear regression models. After adjusting for sex, age, ethnicity, country, and control/sibling status, childhood trauma (β for positive dimension: 0.13, negative: 0.49, depressive: 0.26) and stressful life events (positive: 0.08, negative: 0.16, depressive: 0.17) were associated with the three dimensions. Lower social capital was associated with the negative and depression dimensions (negative: 0.26, depressive: 0.13), and self-reported discrimination experiences with the positive dimension (0.06). Our findings are in favor of independent, cumulative and non-specific influences of social adversities in subclinical psychosis in non-clinical populations, without arguments for E × E interactions.     

Cannabis use in psychotic patients.

OBJECTIVE: The purpose of this study was to examine the level of cannabis use in psychotic patients admitted to two acute admission wards in New Zealand. Symptomatology was investigated using the Brief Psychiatric Rating Scale (BPRS). METHOD: During a 1 -month period, all acute admissions to Tokanui Hospital with psychosis were interviewed and symptoms rated on the BPRS (n = 35). Cannabis use was recorded with a questionnaire and urine test. Those positive for cannabis were compared to those negative. RESULTS: Thirty patients (86%) had tried cannabis at least once and 11 (31%) were positive on urine screen. Those with positive urine tests were significantly more likely to use cannabis most days (p < 0.001). This positive urine test group was less likely to be thought disordered, suspicious or deluded (as measured by the BPRS). CONCLUSIONS: Cannabis use was widespread in this sample of patients with psychosis and may affect their symptomatology. Larger studies are needed to examine these associations in more detail.     

Diagnostic value of the DSM and ICD categories of psychosis: an evidence-based approach

Background: It is generally assumed that the distinction between affective and non-affective psychosis occasioned by modern diagnostic criteria provides a useful symptomatic contrast. Method: In a sample of 708 patients with chronic psychosis, the distinction of lifetime DSM-III-R and ICD-10 diagnoses of affective versus non-affective psychosis was used as a diagnostic test to detect lifetime presence of depressive, manic, positive, negative and disorganisation symptoms. Results: A manic or depressive affective diagnosis was a perfect test to diagnose the presence of manic and depressive symptoms, as evidenced by very high diagnostic likelihood ratios. However, this test result was based solely on the inclusion criterion that patients with affective psychosis must have affective symptoms (guaranteeing high specificity and high likelihood ratios), and ignored the fact that patients with non-affective psychosis also had high affective symptom scores (low sensitivity). Furthermore, a non-affective psychotic diagnosis was a very poor test to diagnose correctly the presence of positive, negative and disorganisation symptoms in comparison with an affective psychotic diagnosis. In general, the DSM-III-R categories performed somewhat better as a diagnostic test than those of ICD-10. Conclusion: The evidence for true diagnostic value of the distinction between affective and non-affective psychotic diagnoses is weak. Rather, the distinction appears to obscure natural overlap between the symptom dimensions of the different diagnostic categories.     

Reasons for cannabis use in psychosis

OBJECTIVE: To examine the reasons for cannabis use among individuals with psychotic disorders. METHOD: Forty-nine people with psychotic disorders in treatment with community health centres in Northern Sydney were interviewed to collect information about their experience of antipsychotic side-effects and their influence on cannabis use. Other information collected on cannabis use included: amount and frequency, effects of use and other general reasons given for use. RESULTS: It was found that boredom, social motives, improving sleep, anxiety and agitation and symptoms associated with negative psychotic symptoms or depression were the most important motivators of cannabis use. Positive symptoms of psychosis and antipsychotic side-effects that were not associated with anxiety, were not important motivators of cannabis use. CONCLUSIONS: As cannabis use may precipitate relapse in this population, it is important to reduce these motivators of use. Clinician's must assess and treat these problems, thus reducing the need for patients to self-medicate with cannabis, and therefore reducing the risk of relapse.     

Schizophrenia and the Environment: Within-Person Analyses May be Required to Yield Evidence of Unconfounded and Causal Association—The Example of Cannabis and Psychosis

Hypotheses about the link between cannabis use and psychosis apply to the within-person level but have been tested mostly at the between-person level. We used a within-person design, in which a person serves as his own control, thus removing the need to consider confounding by any fixed (genetic and nongenetic) characteristic to study the prospective association between cannabis use and the incidence of attenuated psychotic experiences, and vice versa, adjusted for time-varying confounders. We combined 2 general population cohorts (at baseline: Early Developmental Stages of Psychopathology Study, n = 1395; Netherlands Mental Health Survey and Incidence Study-2, n = 6603), which applied a similar methodology to study cannabis use and attenuated psychotic experiences with repeated interviews (T0, T1, T2, and T3) over a period of approximately 10 years. The Hausman test was significant for the adjusted models, indicating the validity of the fixed-effects model. In the adjusted fixed-effects model, prior cannabis use was associated with psychotic experiences (aOR = 7.03, 95% CI: 2.39, 20.69), whereas prior psychotic experiences were not associated with cannabis use (aOR = 0.59, 95% CI: 0.21, 1.71). Longitudinal studies applying random-effects models to study associations between risk factors and mental health outcomes, as well as reverse causality, may not yield precise estimates. Cannabis likely impacts causally on psychosis but not the other way round.     

Psychotic-like experiences and depressive symptoms in a community sample of adolescents

Purpose

Studies of psychotic-like experiences (PLEs) within community samples of adolescents have explored predominantly positive experiences. There is a paucity of research examining the prevalence and correlates of negative PLEs, and whether particular subtypes of negative PLEs can be identified among the general population of adolescents. This study examined the association of both positive and negative PLEs with depressive symptoms, including detailed analysis of subtypes of positive and negative psychosis dimensions.

Method

A community sample of 777 adolescents (50.9% girls: mean age 14.4 years) completed a questionnaire assessing positive and negative PLEs and depressive symptoms.

Results

Principal component factor analysis identified four factors of positive symptoms (persecutory ideation, grandiose thinking, first-rank/hallucinatory experiences and self-referential thinking), and three factors of negative symptoms (social withdrawal, affective flattening, and avolition). Depressive symptoms were associated positively with persecutory ideation, first-rank/hallucinatory experiences, social withdrawal, and avolition, whereas grandiose thinking related negatively with depressive symptoms. Neither self-referential thinking nor affective flattening related to self-reported depression.

Conclusions

These findings support the view that not all types of positive and negative PLEs in adolescence are associated with depression and, therefore, they may not confer the same vulnerability for psychotic disorders.     

Cannabis abuse and risk for psychosis in a prodromal sample

The goal of the present study was to examine the rate of cannabis use among participants in the Cognitive Assessment and Risk Evaluation (CARE) Program, a longitudinal program for individuals who are "at risk" for developing a psychotic disorder. Cannabis abuse was assessed in 48 individuals identified as at risk for psychosis based on subsyndromal psychotic symptoms and/or family history. At 1 year follow-up, 6 of the 48 (12.5%) at risk subjects had made the transition to psychosis. Of the 32 subjects who had no use or minimal cannabis use, one subject (3.1%) converted to psychosis. Of the 16 subjects who met criteria for cannabis abuse/dependence, five (31.3%) converted to psychosis. The results show a significant association between cannabis abuse and conversion to psychosis in this sample. Nicotine use was also found to be significantly associated with later conversion. The significant associations between cannabis and nicotine abuse and conversion to psychosis in individuals at risk for schizophrenia suggest that early identification and intervention programs should screen for and provide education about the deleterious effects of these substances.     

COMT ValMet moderation of cannabis-induced psychosis: a momentary assessment study of 'switching on' hallucinations in the flow of daily life

Objective: A functional polymorphism in the catechol‐o‐methyltransferase gene (COMT Val¹⁵⁸Met) may moderate the psychosis‐inducing effects of cannabis. In order to extend this finding to dynamic effects in the flow of daily life, a momentary assessment study of psychotic symptoms in response to cannabis use was conducted. Method: The experience sampling technique was used to collect data on cannabis use and occurrence of symptoms in daily life in patients with a psychotic disorder (n = 31) and healthy controls (n = 25). Results: Carriers of the COMT Val¹⁵⁸Met Val allele, but not subjects with the Met/Met genotype, showed an increase in hallucinations after cannabis exposure, conditional on prior evidence of psychometric psychosis liability. Conclusion: The findings confirm that in people with psychometric evidence of psychosis liability, COMT Val¹⁵⁸Met genotype moderates the association between cannabis and psychotic phenomena in the flow of daily life.     

Dimensions underlying psychotic and manic symptomatology: Extending normal-range personality traits to schizophrenia and bipolar spectra

Objective

Covariance among psychiatric disorders can be accounted for by higher-order internalizing, externalizing, and psychosis dimensions, but placement of bipolar disorder within this framework has been inconsistent. Moreover, whether deviations in normal-range personality can explain psychosis and vulnerability to severe mood lability, as seen in schizophrenia and bipolar disorder, remains unclear.

Methods

Exploratory factor analysis of interviewer-rated clinical symptoms in patients with schizophrenia or bipolar disorder, their first-degree biological relatives, and nonpsychiatric controls (total N = 193), followed by examination of associations between symptom dimensions and self reports on personality questionnaires.

Results

Covariance in symptoms was accounted for by five factors: positive symptoms of psychosis, negative symptoms of psychosis, disorganization, mania, and depression/anxiety. Schizophrenia and bipolar patients/relatives reported elevated negative emotionality and absorption and lower positive emotionality relative to controls. Personality did not differ between schizophrenia and bipolar patients/relatives, but there was a different pattern of associations between symptoms and personality in these groups.

Conclusions

Discrete dimensions reflecting psychotic, manic, and depressive symptoms emerge when a broad set of clinical symptoms is examined in a sample overrepresented by psychotic experiences and affective disturbances. Although normal-range personality traits index common phenotypes spanning schizophrenia and bipolar spectra, the same symptoms may carry different significance across disorders.     

Patterns, predictors and impact of substance use in early psychosis: a longitudinal study

OBJECTIVE: The purpose was to determine the prevalence of substance use and its impact on outcome 3 years after presentation for a first-episode of psychosis. METHOD: Subjects were 203 consecutive admissions to an early psychosis program. Assessments included substance use, positive, negative and depressive symptoms and social functioning. Assessments occurred at baseline, and 1-, 2- and 3-year follow-ups. RESULTS: The prevalence of substance misuse was high with 51% having a substance use disorder (SUD), 33% with cannabis SUD and 35% with an alcohol SUD. Numbers with an alcohol SUD declined considerably by 1 year and for cannabis SUD by 2 years. Substance misuse was significantly associated with male gender, young age and age of onset and cannabis misuse with increased positive symptoms. CONCLUSION: This study confirms the high rates of substance misuse, in particular cannabis, in first-episode psychosis. It further demonstrates that these rates can be reduced.