Abstract
Background
Cannabis is a drug largely used by First Episode Psychosis (FEP) patients. Also, cannabis use in adolescence is related to higher risk and earlier onset of psychosis. Some studies showed that the earlier onset of psychosis may be related to reduction of cortical thickness in non-affective psychosis patients. The impact on specific diagnosis in FEP patients (affective and non-affective) has not been previously explored. We aim to verify if affective and non-affective psychosis are differentially related to cannabis use and age of psychosis onset.
Methods
Our cohort comprised 175 first-episode individuals assessed at admission of the psychiatric emergency service and reassessed in 3 follow up points. Diagnosis was performed according the Structured Clinical Interview for DSM-IV (SCID-1) applied by trained psychiatrists. The age of psychotic onset was determined during the interview as the first period the symptoms reached severity allowing a psychotic disorder diagnosis. Cannabis use variables were collected from the cannabis section of Addiction Severity Index-6, and the age of first cannabis use was dichotomized in before and after 16 years. Specific diagnosis (affective, non-affective) was extracted according SCID-I diagnosis. Also, we defined drug-induced psychosis as a third group of comparison. We used R-Studio for all data analysis.
Results
The mean age of our sample was 25.42 (SD=7.12) years, mean age of psychosis onset was 24.65 (SD=7.16) years and 65.0% of the subjects were male. The non-affective psychosis (65.6%) was the most prevalent specific diagnosis, followed by affective psychosis (28.1%).
Cannabis use was reported by 41.2% of the individuals, and 53.8% of them used cannabis before 16 years. Those who used cannabis in adolescence had a lower mean age of psychotic onset, however, the mean comparison was not significant (CI 95: -7.17 to 0.69). There was no association between the specific diagnosis, cannabis variables and age of psychosis onset. Those who used cannabis before 16 years had higher prevalence of drug-induced psychosis (X-squared = 13.907, df = 2, p-value = 0.007) in comparison with those who used after.
Discussion
The individuals who reported adolescence cannabis use had lower mean of psychosis onset age, but we could not find statistical support to validate our initial hypothesis: that non-affective psychosis is related to age of psychosis onset. The association between drug-induced psychosis and use of cannabis before 16 years reinforces the risk of cannabis misuse in adolescence.