Disentangling schizophrenia spectrum disorders.

Abstract

Dear Editor, In the recent article published in Acta Psychiatrica Scandinavica, Belbasis and colleagues have taken an ambitious step toward a better understanding of schizophrenia spectrum disorders (SSDs) 1. In their umbrella review – a systematic evaluation of systematic reviews – the authors identified 41 reviews examining 98 associations exploring potential risk factors and biomarkers for SSDs. They found that only one risk factor (history of obstetric complication) demonstrated ‘convincing’ evidence, while three additional risk factors (exposure to childhood adversities, exposure to stressful events during adulthood, and cannabis use) and one biomarker (serum folate level) showed ‘highly suggestive’ evidence. In the sensitivity analysis consisting of only prospective cohort studies, cannabis use and exposure to childhood adversities demonstrated a temporal relationship between exposure and outcome. No prospective studies have examined the other three associations (obstetric complication, exposure to stressful events during adulthood, and serum folate level).