Psychotic experiences, alcohol–cannabis abuse, stressful events and familial risk is associated with onset of clinical psychosis: Evidence from a 6-year longitudinal population-based cohort

Abstract

Introduction

Both clinical and subclinical psychosis is probably a consequence of underlying genetic and environmental interactions.

Objectives

Defining differential impact of environmental/familial risk factors and psychotic experiences across the onset of clinical psychosis.

Aims

To assess mental health outcomes in a 6-year follow-up of a representative general population sample with a special focus on extended psychosis phenotype.

Methods

Addresses were contacted in multistage clustered area probability sampling frame covering 9 districts and 302 neighbourhoods (n: 4011) at baseline (T₁) and 6 years after (n: 2142) (T₂). Psychotic experiences were screened with Composite International Diagnostic Interview and probable cases were re-interviewed with SCID-I. Relations were tested using logistic regression models.

Results

Of subclinical psychotic symptoms at baseline, 6.4% transitioned to clinical psychosis; 44.4% persisted, 90.2% transitioned to any DSM disorder. Of newly onset clinical psychosis at T₂, 62.8% had subclinical psychotic expressions at baseline. The risk of developing clinical psychosis was greater in those with baseline subclinical psychotic experiences, alcohol–cannabis abuse, stressful-forensic event history and family history of mental disorders. Most of risk factors associated with psychosis proneness at T₁ were also associated with clinical psychotic outcome at T₂ (Table 1).

Conclusions

Psychotic experiences takes attention for the risk to develop psychosis due to underlying genetic and environmental interactions; also may be an important risk factor to develop any mental disorder.

Disclosure of interest

The authors have not supplied their declaration of competing interest.

Table 1 Associations between independent variables and newly onset clinical psychosis at T ₂.

^* Adjusted for age, sex, education level and health insurance status.