Cannabis use disorders in schizophrenia: Effects on cognition and symptoms

Abstract

Objective Despite the controversy surrounding the possible causal link between cannabis use and the onset of schizophrenia (SZ), data seeking to elucidate the effect of cannabis use disorders (CUD) on the clinical presentation of SZ have produced mixed results. Although several studies have suggested that CUD in patients with SZ may be associated with variation in cognitive function, clinical presentation and course of illness, the effects have been inconsistent. Methods We retrospectively ascertained a large cohort (N = 455) of SZ patients with either no history of a CUD (CUD−; N=280) or a history of CUD (CUD+; N=175). Groups were initially compared on key demographic variables including sex, race, age, age at onset of SZ, parental socioeconomic status, premorbid IQ, education level and global assessment of functioning. Covarying for any observed differences in demographic variables, we then compared groups on lifetime measures of psychotic symptoms as well as a brief battery of neurocognitive tests. Results Compared to the CUD− group the CUD+ group demonstrated significantly better performance on measures of processing speed (Trail Making Test A and B), verbal fluency (animal naming) and verbal learning and memory (California Verbal Learning Test). Moreover, the CUD+ group had better GAF scores than the CUD− group. Conclusions Collectively, these findings suggest that SZ patients with comorbid CUD may represent a higher functioning subgroup of SZ. Future prospective studies are needed to elucidate the nature of this relationship.

Cannabis and cognitive performance in psychosis: a cross-sectional study in patients with non-affective psychotic illness and their unaffected siblings

“…In contrast with our finding of worse processing speed in current users, the majority of studies in schizophrenia patients reported either absent, or even positive effects of both current and lifetime cannabis use on visual processing speed (Sevy et al 2007 ;Jockers-Scherubl et al 2007 ;Coulston et al 2007a ;Schnell et al 2009 ;DeRosse et al 2010). Positive associations in those studies might have been driven by higher pre-morbid cognitive functioning in cannabis-using patients (Fried et al 2005 ;Schnell et al RST Acc, Response Shifting Task accuracy ; CPT RT, Continuous Performance Task-HQ reaction time ; CPT Acc, CPT-HQ accuracy ; DS coding, Wechsler Adult Intelligence Scale-Third Edition (WAIS-III) digit-symbol coding ; Arithm, WAIS-III arithmetic ; Inform, WAIS-III information ; Block, WAIS-III block design ; Affect Rec, Degraded Facial Affect Recognition total score ; Face Rec, Benton Face Recognition ; Hinting, Hinting task ; F, test statistic from mixed-model regression analyses ; df, degrees of freedom.…”

Age at onset of non-affective psychosis in relation to cannabis use, other drug use and gender

“…The survival curve from the study of González-Pinto et al (2008), with comparable subgroups of patients, shows a similar pattern. This may also explain why some studies in schizophrenia patients did not find differences in age at onset between cannabis users and non-users : the age at onset of psychosis in these studies was around 20 years, which is earlier than the age range where differences occurred in our study (Bersani et al 2002 ;DeRosse et al 2010 ;Goldberger et al 2010). It may also explain why the absolute differences in age at onset between cannabis users and non-users differs substantially across studies.…”

Cannabis users have higher premorbid IQ than other patients with first onset psychosis

“…e l s e v i e r . c o m / l o c a t e / s c h r e s et al, Sevy et al, 2007;DeRosse et al, 2010;Ringen et al, 2010;Yücel et al, 2010;Ringen et al, 2013) that have incidentally examined premorbid IQ in psychosis in relation to cannabis use have reported inconsistent findings, probably due to their small sample size and other methodological problems.…”