Cannabis-induced psychosis and subsequent schizophrenia-spectrum disorders: follow-up study of 535 incident cases
Mikkel Arendt, Raben Rosenberg, Leslie Foldager, Gurli Perto, Povl Munk‐Jørgensen
The British Journal of Psychiatry November 30, 2005 DOI: 10.1192/bjp.187.6.510 (opens in new tab)
Study at a glance
AI-extracted from the abstract| Characteristics | Observational cohort Peer reviewed |
|---|---|
| Sample size | 535 |
| Population | Patients treated for cannabis-induced psychotic symptoms in Denmark between 1994 and 1999, without prior psychotic symptoms |
| Duration | At least 3 years of follow-up |
| Topics | Cannabis |
| Citations | 258 |
| Key findings | Schizophrenia-spectrum disorders were diagnosed in 44.5% of the sample, and new psychotic episodes of any type in 77.2%. Diagnosis was often delayed, with 47.1% receiving a schizophrenia-spectrum diagnosis more than a year after initial treatment. Patients developed schizophrenia at an earlier age than the comparison group (males, 24.6 vs. 30.7 years; females, 28.9 vs. 33.1 years). |
Abstract
Background: Few studies have examined samples of people with cannabis-induced psychotic symptoms.
Aims: To establish whether cannabis-induced psychotic disorders are followed by development of persistent psychotic conditions, and the timing of their onset.
Method: Data on patients treated for cannabis-induced psychotic symptoms between 1994 and 1999 were extracted from the Danish Psychiatric Central Register. Those previously treated for any psychotic symptoms were excluded. The remaining 535 patients were followed for at least 3 years. In a separate analysis, the sample was compared with people referred for schizophrenia-spectrum disorders for the first time, but who had no history of cannabis-induced psychosis.
Results: Schizophrenia-spectrum disorders were diagnosed in 44.5% of the sample. New psychotic episodes of any type were diagnosed in 77.2%. Male gender and young age were associated with increased risk. Development of schizophrenia-spectrum disorders was often delayed, and 47.1% of patients received a diagnosis more than a year after seeking treatment for a cannabis-induced psychosis. The patients developed schizophrenia at an earlier age than people in the comparison group (males, 24.6 v. 30.7 years, females, 28.9 v. 33.1 years).
Conclusions: Cannabis-induced psychotic disorders are of great clinical and prognostic importance.