Patients with schizophrenia spectrum disorders and substance use may have an earlier onset of illness compared to those without substance use. Most previous studies have, however, too small samples to control for confounding variables and the effect of specific types of substances. The present study aimed to examine the relationship between substance use and age at onset, in addition to the influence of possible confounders and specific substances, in a large and heterogeneous multisite sample of patients with schizophrenia spectrum disorders.
The patients (N=1119) were recruited from catchment areas in Oslo, Stavanger and Bergen, Norway, diagnosed according to DSM-IV and screened for substance use history. Linear regression analysis was used to examine the relationship between substance use and age at onset of illness.
Patients with substance use (n=627) had about 3years earlier age at onset (23.0years; SD 7.1) than the abstinent group (n=492; 25.9years; SD 9.7). Only cannabis use was statistically significantly related to earlier age at onset. Gender or family history of psychosis did not influence the results.
Cannabis use is associated with 3years earlier onset of psychosis.
Knowing the prevalence and characteristics of auditory verbal hallucinations (AVH) in adolescents is important for estimations of need for mental health care and assessment of psychosis risk. In this report we assess the prevalence of AVH in a population-based sample of 16-19 years old Norwegian adolescents (n = 9,646, 46.4% male) using two items assessing AVH (from the extended Launay-Slade Hallucination Scale). The prevalence of hearing a voice speaking thoughts aloud was 10.6%. The prevalence of being troubled by voices was 5.3%, showing that negative emotionality about AVH is less frequent than the experience of hearing voices. Female respondents had slightly increased risk for being troubled by voices than males (odds ratio = 1.3), while age did not modulate prevalence. This AVH prevalence is in line with earlier reports in smaller samples of adolescents and indicates that AVH are not uncommon in this period of life. Further longitudinal studies are needed to investigate the value of AVH in predicting psychiatric disorder.