High-potency cannabis and the risk of psychosis

Forti, Marta Di; Morgan, Craig; Dazzan, Paola; Pariante, Carmine M.; Mondelli, Valeria; Marques, Tiago Reis; Handley, Rowena; Luzi, Sonija; Russo, Manuela; Paparelli, Alessandra; Butt, Alexander; Stilo, Simona A.; Wiffen, Ben; Powell, John; Murray, Robin M.

doi:10.1192/bjp.bp.109.064220

Cited by 498 publications

(422 citation statements)

References 15 publications

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“…We investigated experiences reported both during and after cannabis intoxication, which were collected with a five-point Likert scale (from rarely or never to always) and a subjective rating of the quality of that experience ('good', 'bad' or 'neutral'). Contrary to the original version of the CEQ (Barkus et al 2006), which included 55 experiences, the CEQ mv (Di Forti et al 2009) includes only 14 items to reduce respondent burden (which was selected following factor analyses; Table 2). …”

Section: Methodsmentioning

confidence: 99%

“…This study utilized a subsample of the Genetic and Psychosis (GAP) sample (Di Forti et al 2009) Wing et al 1990) were used to clarify symptomatology during the month before the assessment. Patients who met the diagnostic criteria for organic psychosis (ICD-10, F09) were excluded from the cohort.…”

Section: Samplementioning

confidence: 99%

“…Patients who met the diagnostic criteria for organic psychosis (ICD-10, F09) were excluded from the cohort. The control group was recruited from the same area of South-East London; those who met criteria for a psychotic disorder or with a previous diagnosis of psychotic illness were excluded (Di Forti et al 2009). …”

Section: Samplementioning

confidence: 99%

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Differences in cannabis-related experiences between patients with a first episode of psychosis and controls

et al. 2015

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Background. Many studies have reported that cannabis use increases the risk of a first episode of psychosis (FEP). However, only a few studies have investigated the nature of cannabis-related experiences in FEP patients, and none has examined whether these experiences are similar in FEP and general populations. The aim of this study was to explore differences in self-reported cannabis experiences between FEP and non-psychotic populations.Method. A total of 252 subjects, who met International Classification of Diseases (ICD)-10 criteria for FEP, and 217 controls who reported cannabis use were selected from the Genetics and Psychosis (GAP) study. The Medical Research Council Social Schedule and the Cannabis Experience Questionnaire were used to collect sociodemographic data and cannabis use information, respectively.Results. Both 'bad' and 'enjoyable' experiences were more commonly reported by FEP subjects than controls. Principal components factor analysis identified four components which explained 62.3% of the variance. Linear regression analysis on the whole sample showed that the type of cannabis used and beliefs about the effect of cannabis on health all contributed to determining the intensity and frequency of experiences. Linear regression analysis on FEP subjects showed that the duration of cannabis use and amount of money spent on cannabis were strongly related to the intensity and frequency of enjoyable experiences in this population.Conclusions. These results suggest a higher sensitivity to cannabis effects among people who have suffered their first psychotic episode; this hypersensitivity results in them reporting both more 'bad' and 'enjoyable' experiences. The greater enjoyment experienced may provide an explanation of why FEP patients are more likely to use cannabis and to continue to use it despite experiencing an exacerbation of their psychotic symptoms.

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Section: Methodsmentioning

confidence: 99%

Section: Samplementioning

confidence: 99%

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Differences in cannabis-related experiences between patients with a first episode of psychosis and controls

et al. 2015

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“…Cannabis use has been repeatedly shown to be a risk factor for the development of psychosis (Henquet et al, 2005;Moore et al, 2007;Potvin and Amar, 2008;Di Forti et al, 2009;Casadio et al, 2011).…”

Section: Introductionmentioning

confidence: 99%

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

Ferraro

Russo

O’Connor

et al. 2013

Schizophrenia Research

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a b s t r a c t a r t i c l e i n f oBackground: A number of studies have reported that patients with psychosis who use cannabis have better cognitive performance than those who do not. This is surprising as cannabis can impair cognition in healthy subjects. An obvious question is whether the better current performance of psychotic patients who have used cannabis is a reflection of their having a higher premorbid IQ than those psychotic patients who haven't used cannabis. Aim: In a sample of patients at their first episode of psychosis, we tested the hypothesis that patients who smoked cannabis would have a higher premorbid IQ than patients who did not. Methodology: 279 participants (119 patients and 160 healthy controls) were assessed in order to obtain current and premorbid IQ measures and detailed information on cannabis use. We examined the association between cannabis use and both premorbid and current IQ in patients and controls. Results: Patients who had ever smoked cannabis had significantly higher current (p b .001) and premorbid IQ (p = .004) compared to patients who had never used cannabis. This difference was not found among controls. Conclusions: These findings suggest that the better cognitive performance of patients with their first episode of psychosis who have used cannabis compared with those who haven't is due to the better premorbid IQ of the former.

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“…This is consistent with earlier examinations of the cannabis–psychosis relationship (Andreasson, Allebeck, Engstrom, & Rydberg, 1987; Arseneault, Cannon, Witton, & Murray, 2004; Arseneault et al., 2002; Compton et al., 2009; Di Forti et al., 2009, 2014; Kelley et al., 2016; McLaren, Silins, Hutchinson, Mattick, & Hall, 2010; Moore et al., 2007) (for a meta‐analysis, see Large, Sharma, Compton, Slade, & Nielssen, 2011). The effect of gender on AoP was significant in our study, with males being at risk of developing psychosis earlier than females.…”

Section: Discussionmentioning

confidence: 99%

Investigation of the COMT Val158Met variant association with age of onset of psychosis, adjusting for cannabis use

et al. 2017

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Objective COMT rs4680 (Val158Met) genotype moderates the effect of cannabis on the age of onset of psychosis (AoP). We investigated the association between rs4680 and AoP, after adjusting for relevant covariates, in a Canadian Caucasian sample.MethodsOne hundred and sixty‐nine subjects with psychosis were recruited. AoP, defined as age of DSM‐IV diagnosis was established using the Structured Clinical Interview for DSM‐IV. Cannabis use data were collected using a self‐report computerized questionnaire. DNA was extracted from saliva and genotyping of the COMT Val158Met polymorphism was done by SNaPshot and TaqMan assays. Logistic regression and Kaplan–Meier analysis results are reported.ResultsIn those who had used cannabis before 20 years of age, rs4680 had a trend level effect on AoP (median AoP: Val/Val < Val/Met < Met/Met 19.37, 20.95, 21.24 years, respectively; log‐rank test p = .051).ConclusionOur data are indicative of the need to further investigate the association between the COMT rs4680 variant and AoP in the context of adolescent cannabis use.

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High-potency cannabis and the risk of psychosis

Cited by 498 publications

References 15 publications

Differences in cannabis-related experiences between patients with a first episode of psychosis and controls

Differences in cannabis-related experiences between patients with a first episode of psychosis and controls

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

Investigation of the COMT Val158Met variant association with age of onset of psychosis, adjusting for cannabis use

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