Neurocognitive and social cognitive predictors of cannabis use in first-episode psychosis

Conceptualization and characterization of "primary" and "secondary" cognitive impairment in schizophrenia

Cognitive impairment represents one of the core features of schizophrenia, involves both neurocognition and social cognition domains, and has a significant negative impact on real-world functioning. The present review provides a framework for the conceptualization and characterization of "primary" and "secondary" cognitive impairment in schizophrenia. In this conceptualization, primary cognitive impairment can be defined as a consequence of the neurobiological alterations that underlie psychopathological manifestations of the disorder, while secondary cognitive impairment can be defined as the results of a source issue that has a negative impact on cognitive performance. Sources of secondary cognitive impairment are frequent in people with schizophrenia and include several different factors, such as positive and negative symptoms, depressive symptoms, autistic symptoms, pharmacotherapy, substance abuse, metabolic syndrome, social deprivation, and sleep disorders. It can be hypothesized that secondary cognitive impairment may be improved by effectively resolving the source issue, while primary cognitive impairment may benefit from dedicated treatment. Further research is required to confirm this hypothesis, to better characterize the distinction between primary and secondary cognitive impairment in a clinical and in a neurobiological perspective, and to evaluate the impact of systematically assessing and treating secondary cognitive impairment.

The association between cannabis use and facial emotion recognition in schizophrenia, siblings, and healthy controls: Results from the EUGEI study

Schizophrenia is frequently accompanied with social cognitive disturbances. Cannabis represents one established environmental factor associated with the onset and progression of schizophrenia. The present cross-sectional study aimed to investigate the association of facial emotion recognition (FER) performance with cannabis use in 2039 patients with schizophrenia, 2141 siblings, and 2049 healthy controls (HC). FER performance was measured using the Degraded Facial Affect Recognition Task (DFAR). Better FER performance as indicated by higher DFAR-total scores was associated with lifetime regular cannabis use in schizophrenia (B = 1.36, 95% CI 0.02 to 2.69), siblings (B = 2.17, 95% CI 0.79 to 3.56), and HC (B = 3.10, 95% CI 1.14 to 5.06). No associations were found between DFAR-total and current cannabis use. Patients with schizophrenia who started to use cannabis after the age of 16 showed better FER performance than patients who started earlier (B = 2.50, 95% CI 0.15 to 4.84) and non-users (B = 3.72, 95 CI 1.96 to 5.49). Better FER performance was found also in siblings who started to use cannabis after 16 compared to non-users (B = 2.37, 95% CI 0.58 to 4.16), while HC using cannabis performed better than non-users at DFAR-total regardless of the age at onset. Our findings suggest that lifetime regular cannabis use may be associated with better FER regardless of the psychosis risk, but that FER might be moderated by age at first use in people with higher genetic risk. Longitudinal studies may clarify whether there is a cause-and-effect relationship between cannabis use and FER performance in psychotic and non-psychotic samples.

Social cognition and its relationship with sociodemographic, clinical, and psychosocial variables in first-episode psychosis

People with first episode of psychosis (FEP) show deficits in social cognition, which have been linked to several sociodemographic, clinical, and psychosocial variables. The aim of the present research was to study social cognition as a whole measure in people with FEP comparing it with a healthy control sample, to study gender differences, and to examine the relationship between sociodemographic, clinical, and psychosocial variables and social cognition in the onset of psychosis. A descriptive, cross-sectional study was performed. The study sample consisted of 63 people (18 females; 45 males) with a diagnosis of FEP and a healthy control group (78 participants: 38 females; 40 males). All the participants were assessed with the social cognitive domain of the MATRICS Consensus Cognitive Battery (MCCB) and several questionnaires related to studied variables. Our results indicated that compared with healthy controls, people with FEP showed social cognition deficits. Furthermore, premorbid IQ was the most relevant variable in social cognition performance in FEP sample. The findings of the present research may be taken into account in clinical practice to improve the intervention with people with FEP.

The relationship between cannabis use and cognition in people diagnosed with first-episode psychosis

Cannabis use is highly prevalent among young people diagnosed with first-episode psychosis (FEP), however, its impact on cognition is still unclear. The aim of the present study was to examine the association of cannabis use with cognition in people diagnosed with FEP. We extended previous research findings by operationalising the comorbid cannabis use, considering recency of cannabis use and use of other illicit substances and including people with a broad spectrum of psychotic diagnoses. A total of 89 people diagnosed with FEP were interviewed about their history of substance use and completed a cognitive test battery assessing verbal memory, verbal fluency and attention. Sixty-one participants were lifetime cannabis users (CU; ≥three times per week for ≥four weeks; 68.5%) and 28 were cannabis non-users (CNU; 31.5%). CU were significantly more likely to be male and exhibited significantly more positive symptoms than CNU. In contrast, CNU displayed significantly more negative symptoms than CU. There were no differences between CU and CNU on neurocognitive tasks of verbal memory, verbal fluency and attention. In conclusion, there was no indication that cannabis use was associated with cognitive impairments in people diagnosed with FEP.

Premorbid Adjustment and IQ in Patients With First-Episode Psychosis: A Multisite Case-Control Study of Their Relationship With Cannabis Use

Psychotic patients with a lifetime history of cannabis use generally show better cognitive functioning than other psychotic patients. Some authors suggest that cannabis-using patients may have been less cognitively impaired and less socially withdrawn in their premorbid life. Using a dataset comprising 948 patients with first-episode psychosis (FEP) and 1313 population controls across 6 countries, we examined the extent to which IQ and both early academic (Academic Factor [AF]) and social adjustment (Social Factor [SF]) are related to the lifetime frequency of cannabis use in both patients and controls. We expected a higher IQ and a better premorbid social adjustment in psychotic patients who had ever used cannabis compared to patients without any history of use. We did not expect such differences in controls. In both patients and controls, IQ was 3 points higher among occasional-users than in never-users (mean difference [Mdiff] = 2.9, 95% CI = [1.2, 4.7]). Both cases and control daily-users had lower AF compared to occasional (Mdiff = -0.3, 95% CI = [-0.5; -0.2]) and never-users (Mdiff = -0.4, 95% CI = [-0.6; -0.2]). Finally, patient occasional (Mdiff = 0.3, 95% CI = [0.1; 0.5]) and daily-users (Mdiff = 0.4, 95% CI = [0.2; 0.6]) had better SF than their never-using counterparts. This difference was not present in controls (Fgroup*frequency(2, 2205) = 4.995, P = .007). Our findings suggest that the better premorbid social functioning of FEP with a history of cannabis use may have contributed to their likelihood to begin using cannabis, exposing them to its reported risk-increasing effects for Psychotic Disorders.

Psychosocial interventions for people with both severe mental illness and substance misuse

BACKGROUND

Even low levels of substance misuse by people with a severe mental illness can have detrimental effects.

OBJECTIVES

To assess the effects of psychosocial interventions for reduction in substance use in people with a serious mental illness compared with standard care.

SEARCH METHODS

The Information Specialist of the Cochrane Schizophrenia Group (CSG) searched the CSG Trials Register (2 May 2018), which is based on regular searches of major medical and scientific databases.

SELECTION CRITERIA

We included all randomised controlled trials (RCTs) comparing psychosocial interventions for substance misuse with standard care in people with serious mental illness.

DATA COLLECTION AND ANALYSIS

Review authors independently selected studies, extracted data and appraised study quality. For binary outcomes, we calculated standard estimates of risk ratio (RR) and their 95% confidence intervals (CIs) on an intention-to-treat basis. For continuous outcomes, we calculated the mean difference (MD) between groups. Where meta-analyses were possible, we pooled data using a random-effects model. Using the GRADE approach, we identified seven patient-centred outcomes and assessed the quality of evidence for these within each comparison.

MAIN RESULTS

Our review now includes 41 trials with a total of 4024 participants. We have identified nine comparisons within the included trials and present a summary of our main findings for seven of these below. We were unable to summarise many findings due to skewed data or because trials did not measure the outcome of interest. In general, evidence was rated as low- or very-low quality due to high or unclear risks of bias because of poor trial methods, or inadequately reported methods, and imprecision due to small sample sizes, low event rates and wide confidence intervals. 1. Integrated models of care versus standard care (36 months) No clear differences were found between treatment groups for loss to treatment (RR 1.09, 95% CI 0.82 to 1.45; participants = 603; studies = 3; low-quality evidence), death (RR 1.18, 95% CI 0.39 to 3.57; participants = 421; studies = 2; low-quality evidence), alcohol use (RR 1.15, 95% CI 0.84 to 1.56; participants = 143; studies = 1; low-quality evidence), substance use (drug) (RR 0.89, 95% CI 0.63 to 1.25; participants = 85; studies = 1; low-quality evidence), global assessment of functioning (GAF) scores (MD 0.40, 95% CI -2.47 to 3.27; participants = 170; studies = 1; low-quality evidence), or general life satisfaction (QOLI) scores (MD 0.10, 95% CI -0.18 to 0.38; participants = 373; studies = 2; moderate-quality evidence). 2. Non-integrated models of care versus standard care There was no clear difference between treatment groups for numbers lost to treatment at 12 months (RR 1.21, 95% CI 0.73 to 1.99; participants = 134; studies = 3; very low-quality evidence). 3. Cognitive behavioural therapy (CBT) versus standard care There was no clear difference between treatment groups for numbers lost to treatment at three months (RR 1.12, 95% CI 0.44 to 2.86; participants = 152; studies = 2; low-quality evidence), cannabis use at six months (RR 1.30, 95% CI 0.79 to 2.15; participants = 47; studies = 1; very low-quality evidence) or mental state insight (IS) scores by three months (MD 0.52, 95% CI -0.78 to 1.82; participants = 105; studies = 1; low-quality evidence). 4. Contingency management versus standard care We found no clear differences between treatment groups for numbers lost to treatment at three months (RR 1.55, 95% CI 1.13 to 2.11; participants = 255; studies = 2; moderate-quality evidence), number of stimulant positive urine tests at six months (RR 0.83, 95% CI 0.65 to 1.06; participants = 176; studies = 1) or hospitalisations (RR 0.21, 95% CI 0.05 to 0.93; participants = 176; studies = 1); both low-quality evidence. 5. Motivational interviewing (MI) versus standard care We found no clear differences between treatment groups for numbers lost to treatment at six months (RR 1.71, 95% CI 0.63 to 4.64; participants = 62; studies = 1). A clear difference, favouring MI, was observed for abstaining from alcohol (RR 0.36, 95% CI 0.17 to 0.75; participants = 28; studies = 1) but not other substances (MD -0.07, 95% CI -0.56 to 0.42; participants = 89; studies = 1), and no differences were observed in mental state general severity (SCL-90-R) scores (MD -0.19, 95% CI -0.59 to 0.21; participants = 30; studies = 1). All very low-quality evidence. 6. Skills training versus standard care At 12 months, there were no clear differences between treatment groups for numbers lost to treatment (RR 1.42, 95% CI 0.20 to 10.10; participants = 122; studies = 3) or death (RR 0.15, 95% CI 0.02 to 1.42; participants = 121; studies = 1). Very low-quality, and low-quality evidence, respectively. 7. CBT + MI versus standard care At 12 months, there was no clear difference between treatment groups for numbers lost to treatment (RR 0.99, 95% CI 0.62 to 1.59; participants = 327; studies = 1; low-quality evidence), number of deaths (RR 0.60, 95% CI 0.20 to 1.76; participants = 603; studies = 4; low-quality evidence), relapse (RR 0.50, 95% CI 0.24 to 1.04; participants = 36; studies = 1; very low-quality evidence), or GAF scores (MD 1.24, 95% CI -1.86 to 4.34; participants = 445; studies = 4; very low-quality evidence). There was also no clear difference in reduction of drug use by six months (MD 0.19, 95% CI -0.22 to 0.60; participants = 119; studies = 1; low-quality evidence).

AUTHORS' CONCLUSIONS

We included 41 RCTs but were unable to use much data for analyses. There is currently no high-quality evidence to support any one psychosocial treatment over standard care for important outcomes such as remaining in treatment, reduction in substance use or improving mental or global state in people with serious mental illnesses and substance misuse. Furthermore, methodological difficulties exist which hinder pooling and interpreting results. Further high-quality trials are required which address these concerns and improve the evidence in this important area.

Parcellating cognitive heterogeneity in early psychosis-spectrum illnesses: A cluster analysis

Cognitive impairment is argued to represent a core feature of psychosis-spectrum illnesses. However, within-diagnosis heterogeneity is common, and risk factors for poor cognition remain to be examined after statistically accounting for heterogeneity. Accordingly, we used a data-driven technique (cluster analysis) to empirically-derive cognitive clusters across diagnoses and examined whether concurrent substance use or a history of a neurodevelopmental/behavioral disorder differed between clusters. Data from 135 young help-seekers (aged 12-30 years) with a psychosis-spectrum illness were retrospectively analyzed. Ward's hierarchical cluster analysis classified three cognitive clusters characterized by: (1) normal-range; (2) mixed; and (3) grossly-impaired performance. Despite mostly comparable clinical and demographic measures, cluster 1 had superior socio-occupational functioning and the highest estimated premorbid IQ, followed sequentially by clusters 2 and 3. Proportions of cannabis and amphetamine users did not differ significantly across clusters, nor did rates of patients with a neurodevelopmental/behavioral disorder history. Cluster 3 was however comprised of fewer 'risky' drinkers, possibly reflecting reduced opportunity for social drinking associated with cognitive impairment. Estimated premorbid IQ predicted cluster membership (2 vs. 1 & 3 vs. 1), as did clinician-rated socio-occupational functioning and 'not being enrolled in school or tertiary education' (3 vs. 1). Our results suggest that concurrent substance use and history of a neurodevelopmental/behavioral disorder do not adequately explain cluster-level cognitive variance in this sample. Future work should integrate neurobiological measures associated with cognition (e.g. white matter integrity) to discern whether clusters reflect neurobiological subtypes better representative of pathophysiology than present symptom-based classifications.

Are cannabis-using and non-using patients different groups? Towards understanding the neurobiology of cannabis use in psychotic disorders

A substantial body of credible evidence has accumulated that suggest that cannabis use is an important potentially preventable risk factor for the development of psychotic illness and its worse prognosis following the onset of psychosis. Here we summarize the relevant evidence to argue that the time has come to investigate the neurobiological effects of cannabis in patients with psychotic disorders. In the first section we summarize evidence from longitudinal studies that controlled for a range of potential confounders of the association of cannabis use with increased risk of developing psychotic disorders, increased risk of hospitalization, frequent and longer hospital stays, and failure of treatment with medications for psychosis in those with established illness. Although some evidence has emerged that cannabis-using and non-using patients with psychotic disorders may have distinct patterns of neurocognitive and neurodevelopmental impairments, the biological underpinnings of the effects of cannabis remain to be fully elucidated. In the second and third sections we undertake a systematic review of 70 studies, including over 3000 patients with psychotic disorders or at increased risk of psychotic disorder, in order to delineate potential neurobiological and neurochemical mechanisms that may underlie the effects of cannabis in psychotic disorders and suggest avenues for future research.

Meta-analysis of neurocognition in young psychosis patients with current cannabis use

OBJECTIVE

Adult psychosis patients (i.e. over the age of 25 years) who are also lifetime cannabis users (CANN±) appear to exhibit superior cognition compared to never-using patients (CANN-). The objective of this meta-analysis was to evaluate the cognitive differences between CANN- and patients who currently use cannabis (CANN+) (i.e. during the CANN± patients' cannabis-using stage). Specifically, focusing on young patients under the age of 25 years, the typical stage of both psychosis- and cannabis-onset.

METHOD

Of the 308 studies identified through database searches and secondary referencing, 14 compared neurocognition of CANN+ and CANN- in young people with psychotic disorders (mean age between 15 and 45 years). Effect sizes were extracted using neurocognitive test performance between CANN+ and CANN- and random effects modelling was conducted on pooled ES and moderator analyses.

RESULTS

CANN+ performed worse on several cognitive domains (i.e. premorbid IQ, current IQ, verbal learning, verbal working memory, motor inhibition) compared to CANN-. The association between age and performance in CANN+ cognition was varied, with older age predictive of worse performance in processing speed, sustained attention, verbal memory, and better performance in verbal learning and very fluency. Of note, CANN+ outperformed CANN- in tests of conceptual set-shifting.

CONCLUSION

These results are consistent with previous findings indicating that CANN+ demonstrate poorer neurocognition than CANN-; and that this is exacerbated with increasing age. Our findings demonstrate significant cognitive differences between patients with CANN+ versus CANN- even at early-onset psychosis, which could suggest a different underlying mechanism towards psychosis for cannabis users.

An examination of sex differences in neurocognition and social cognition in first-episode psychosis

Due to the dearth and conflicting findings of previous research, it is unclear whether males and females with first-episode psychosis (FEP) differ in their neurocognitive and social cognitive abilities. The aims of the current study were to investigate whether: (i) there are sex differences in neurocognition and social cognition among young people with FEP; and (ii) they resemble those observed in age-matched healthy controls. The current study involved secondary analysis of data from a previous study in which a large neurocognitive and social cognitive battery was administered to 146 individuals with FEP and 46 healthy controls aged 15-25 years. Seven two-way between-groups multivariate analysis of variances revealed that FEP participants were impaired relative to controls on all cognitive domains. Only one main effect of sex was found with males, regardless of group, outperforming females on verbal comprehension. A significant interaction effect was found for information processing speed with FEP females outperforming FEP males on the Symbol Digit Modalities Test; however, post-hoc analysis of the mean difference was not significant. Despite few sex differences, the current study highlights that cognitive impairment is a key feature of FEP that should be a treatment target in early intervention.

Cannabis-associated psychosis: Neural substrate and clinical impact

Prospective epidemiological studies have consistently demonstrated that cannabis use is associated with an increased subsequent risk of both psychotic symptoms and schizophrenia-like psychoses. Early onset of use, daily use of high-potency cannabis, and synthetic cannabinoids carry the greatest risk. The risk-increasing effects are not explained by shared genetic predisposition between schizophrenia and cannabis use. Experimental studies in healthy humans show that cannabis and its active ingredient, delta-9-tetrahydrocannabinol (THC), can produce transient, dose-dependent, psychotic symptoms, as well as an array of psychosis-relevant behavioral, cognitive and psychophysiological effects; the psychotogenic effects can be ameliorated by cannabidiol (CBD). Findings from structural imaging studies in cannabis users have been inconsistent but functional MRI studies have linked the psychotomimetic and cognitive effects of THC to activation in brain regions implicated in psychosis. Human PET studies have shown that acute administration of THC weakly releases dopamine in the striatum but that chronic users are characterised by low striatal dopamine. We are beginning to understand how cannabis use impacts on the endocannabinoid system but there is much still to learn about the biological mechanisms underlying how cannabis increases risk of psychosis. This article is part of the Special Issue entitled "A New Dawn in Cannabinoid Neurobiology".

The positive link between executive function and lifetime cannabis use in schizophrenia is not explained by current levels of superior social cognition

There has been a growing link between a history of cannabis use and neurocognitive performance in patients with schizophrenia. Fewer neurocognitive deficits may be a marker of the superior social cognition needed to obtain illicit substances, or cannabis use may indicate a distinct path to schizophrenia with less neurocognitive vulnerability. This study sought to determine whether the relationship of cannabis use and executive function exists independently of social cognition. Eighty-seven patients with schizophrenia were administered measures of social cognition and executive function. Social cognition was assessed using the Bell-Lysaker Emotion Recognition Test to measure affect recognition, and the Eyes and Hinting Tests to measure theory of mind. Executive function was assessed by the Mental Flexibility component of the Delis-Kaplan Executive Functioning Scale. The relations between the variables were examined with structural equation modeling. Cannabis use positively related to executive function, negatively related to affect recognition, and had no relationship with theory of mind. There were no indirect effects of other illicit substances on amount of regular cannabis use. Alcohol use was related to worse affect recognition. The relationship between cannabis use and better executive function was supported and was not explained by superior social cognition.

Neurobiological underpinnings and modulating factors in schizophrenia spectrum disorders with a comorbid substance use disorder: A systematic review

Recently there is a growing interest in the interaction of schizophrenia spectrum disorders (SSD) and substance use disorders (SUD), a condition named dual schizophrenia spectrum disorders (SSD+). While previous research has focused on clinical and cognitive aspects, little is known about the impact of comorbidity in the brain structure and functions. Evidence suggests that dual diagnosis patients, including SSD+, show a better neurocognitive functioning during the first years of illness, followed by a serious long-term decline. The initial search retrieved 94 articles, 12 were excluded for being redundant and 49 for not fulfilling the selection criteria. Thirty-three structural and functional neuroimaging studies that compare SSD and SSD+ patients were included. Both groups exhibited more brain alterations, in comparison to only SUD patients and healthy controls. SSD+ patients are less cognitively and emotionally impaired than non-dual SSD, but worse than healthy controls. The neurobiological alterations are prominent in SSD+ after five years of illness or longer. Moreover, SUD characteristics are important modulating factors, contrary to clinical severity or specific SSD diagnosis.

Relationship between duration of untreated psychosis and neurocognition and social cognition in first-episode psychosis

Cognitive impairment is common in first-episode psychosis (FEP); however, the relationship between duration of untreated psychosis (DUP) and neurocognition remains controversial, and no studies have examined the relationship between DUP and social cognition. This study involved secondary data analysis of baseline data from a randomised controlled trial of supported employment; 122 out 146 young people with FEP met inclusion criteria for this study. Results showed that DUP was not associated with neurocognitive or social cognitive performance. Results do not provide support for the neurotoxicity hypothesis of psychosis.

Traditional marijuana, high-potency cannabis and synthetic cannabinoids: increasing risk for psychosis

Epidemiological evidence demonstrates that cannabis use is associated with an increased risk of psychotic outcomes, and confirms a dose-response relationship between the level of use and the risk of later psychosis. High-potency cannabis and synthetic cannabinoids carry the greatest risk. Experimental administration of tetrahydrocannabinol, the active ingredient of cannabis, induces transient psychosis in normal subjects, but this effect can be ameliorated by co-administration of cannabidiol. This latter is a constituent of traditional hashish, but is largely absent from modern high-potency forms of cannabis. Argument continues over the extent to which genetic predisposition is correlated to, or interacts with, cannabis use, and what proportion of psychosis could be prevented by minimizing heavy use. As yet, there is not convincing evidence that cannabis use increases risk of other psychiatric disorders, but there are no such doubts concerning its detrimental effect on cognitive function. All of the negative aspects are magnified if use starts in early adolescence. Irrespective of whether use of cannabis is decriminalized or legalized, the evidence that it is a component cause of psychosis is now sufficient for public health messages outlining the risk, especially of regular use of high-potency cannabis and synthetic cannabinoids.

Opposite Cannabis-Cognition Associations in Psychotic Patients Depending on Family History

The objective of this study is to investigate cognitive performance in a first-episode psychosis sample, when stratifying the interaction by cannabis use and familial or non-familial psychosis. Hierarchical-regression models were used to analyse this association in a sample of 268 first-episode psychosis patients and 237 controls. We found that cannabis use was associated with worse working memory, regardless of family history. However, cannabis use was clearly associated with worse cognitive performance in patients with no family history of psychosis, in cognitive domains including verbal memory, executive function and global cognitive index, whereas cannabis users with a family history of psychosis performed better in these domains. The main finding of the study is that there is an interaction between cannabis use and a family history of psychosis in the areas of verbal memory, executive function and global cognition: that is, cannabis use is associated with a better performance in patients with a family history of psychosis and a worse performance in those with no family history of psychosis. In order to confirm this hypothesis, future research should explore the actual expression of the endocannabinoid system in patients with and without a family history of psychosis.

Differential effects of sex on substance use between first episode psychosis patients and healthy people

BACKGROUND

Substance use in psychosis is an important field of study given that it can be a risk factor for the development of psychosis and can give rise to psychotic symptoms. Studies of substance use in first episode psychosis patients do not frequently assess non-pathological substance consumption among patients, but rather the prevalence of substance abuse or dependence disorders. Moreover, most of these studies do not address the effects of sex in sufficient depth, and the consumption of caffeine or tobacco, which are two of the most frequently used substances, is often not assessed.

OBJECTIVES

The aim of this study was to compare patterns and quantities of substance use between first episode psychosis patients and healthy controls and between men and women, and explore the potential interactive effects between group (patients or controls) and sex.

METHODS

A total of 158 participants (82 first episode psychosis patients and 76 healthy controls) were included in the study. Both adults and adolescents were included in the study. Frequency and amount of use of caffeine, tobacco, alcohol, cannabis, cocaine, hallucinogens, stimulants, and opiates were gathered.

RESULTS

A significant main effect of sex was found for the frequency of use of tobacco (p=.050). Main effects of group were found for the quantity of tobacco (p<.001) and cannabis (p<.001) consumed, as well as main effects of sex for the quantity of alcohol (p=.003) and cannabis (p=.017) consumed. There were also interaction effects between group and sex for the frequency of use of tobacco (p=.005) and cannabis (p=.009), and for the amount of cannabis consumed (p=.049). Qualitative differences between males and females regarding combined substance use are also reported.

CONCLUSIONS

Among patients, men used tobacco more frequently than women, but this sex difference was not the same for the control group, in which women smoked more often than men. Regarding cannabis, men smoked cannabis more frequently and in larger amounts than women, but only in the patients group, whereas no sex differences for cannabis were found for the controls. Main effects of group and sex for tobacco and alcohol, as well as the lack of differences for the frequency and amount of use of caffeine, are also commented. This is the first study to assess the different effects of sex on substance use in first episode psychosis patients and healthy controls.