Background: Patients presenting to psychiatric services with their first episodeof psychosis (FEP) report higher rates of previous cannabis use thanthe general population (Donoghue et al., 2011; Myles, Myles and Large,2016). Evidence suggested that patients suffering from psychosis with a historyof cannabis use have an earlier age of onset of psychosis (AOP) thanthose who never used it (Di Forti et al., 2013).We aim to investigate if the reported association between use of cannabisand AOP is consistent across different countries, once having taken intoaccount different patterns of cannabis use (i.e. frequency of use and ageat first use).Methods: We analysed data on patterns of lifetime cannabis use and AOPfrom FEP=1,149 (61.7% males) from 5 European countries and Brazil partof the European network of national schizophrenia networks studyingEuropean Gene-Environment-Interaction (EUGEI) study.Patients met ICD-10 criteria for psychosis, ascertained by using OPCRIT(McGuffin et al., 1991).The CEQmv (Di Forti et al., 2009) further modified for the EUGEI study,was used to collect data on lifetime frequency of cannabis use (never used/used at least once but less than daily/ everyday use) and age at first use inyears (then dichotomized according to mean age at first use ≤15 years or≥16 years).We used two ANOVAs: age of onset was used as the outcome variable andfrequency of cannabis use and age of first use were respectively enteredas independent predictors, along with country, gender and self-ascribedethnicity.Results: 63.3% of our sample used cannabis at least once in lifetime.Among those who used cannabis in their lifetime, mean age at first use was16.8 years (sd=4.6) and median age was 16 years, 42.3% tried first time cannabisat 15 years or before, 57.7% at 16 years or older. Patients who smoked cannabis on a recreational basis (mean age 29.0; contrast=5.8,CI 95% 4.3, 7.2, p<0.001) and on a daily basis (mean age 26.6;contrast=2.4, CI 95% 0.9, 3.9, p=0.001) had lower age of onset than notusers patients (mean age 34.8) across all countries, once have taken intoaccount gender and ethnicityOnly, those who started using cannabis ≤15 years had an earlier age of onset(25.5 years) than those who started at their 16 years or later (29.5 years),(F(1,683)=37.3, p<0.001). This relationship was the same across differentcountries (p=0.968), and independently influenced by ethnicity (F(5,683)=2.3, p=0.03) but not by gender (p=0.057).Discussion: Our results suggest a generalizable across country and specificeffect of frequency of use and early age at first cannabis use on significantlyanticipate age of psychosis onset in First episode Psychosispatients.
|Number of pages||2|
|Publication status||Published - 2018|