Psychosis risk atlas: six convincing factors, and childhood adversity carries the largest preventable share

Design

Umbrella review of systematic reviews with meta-analyses of observational studies

Population

69 meta-analyses, 970 studies, 221 risk or protective factors

Primary outcome

Association with ICD/DSM non-organic psychotic disorders, graded class I to IV

Effect

6 class I factors (e.g. birthweight under 2,000 g OR 1.77, 95% CI 1.48 to 2.13); childhood adversity PAF 40.7%

An umbrella review pooled 69 systematic reviews and meta-analyses of observational studies, covering 970 studies and 221 putative risk or protective factors for non-organic psychotic disorders, published between 2017 and March 2025. Each association was graded from convincing (class I) to weak (class IV), with sensitivity analyses restricted to prospective studies and using more conservative uncertainty estimates.

Six factors reached class I: Black-African ethnicity in England (OR 4.89), South Asian ethnicity in England (OR 2.15), paternal age under 20 (OR 1.34), birthweight under 2,000 g (OR 1.77) or under 2,500 g (OR 1.50), and a mother with three or more previous pregnancies (OR 1.32). Eighteen more were highly suggestive, including maternal psychosis, first-generation migration, near-daily cannabis use, Toxoplasma gondii seropositivity and a history of ADHD.

For potentially modifiable factors, the review estimated population attributable fractions. Childhood adversity had the largest (about 41%), then Toxoplasma seropositivity (20%), cannabis use 5 to 7 days a week (13%) and the clinical high-risk state (13%). These fractions assume causation, which observational data cannot prove.

The practical value is in history-taking and in where prevention effort might go. The migration and ethnicity findings come from England and reflect social exposures rather than biology; they should not be read across to South Asians living in South Asia.

• Ask about childhood adversity in young people presenting with attenuated psychotic symptoms.
• Record cannabis frequency, not just use: near-daily use carried highly suggestive evidence.
• Note low birthweight and maternal psychiatric history when assessing a first episode.
• Do not read the England ethnicity findings as applying to people living in South Asia.
• Use the class I to IV grading to judge how firmly any single risk factor is established.

Why it matters

It moves prevention from a general aspiration to a ranked list of exposures, with adversity and heavy cannabis use at the top.

Don't overread it

Every included study was observational, so these are associations; the attributable fractions assume causes that have not been proven.

The statistics, in plain English

An odds ratio of 1.77 for birthweight under 2,000 g means the odds of a psychotic disorder were about three-quarters higher, a modest increase on a low baseline. A population attributable fraction of 41% means that if childhood adversity caused psychosis and were removed, about 41% of cases might not occur; that figure assumes causation and is an upper estimate.

Read the rest in the app

You have read your two free briefings this month. The app carries all 27 specialties, every morning, free — and this finding is waiting in it.

Get Daily Doctor — free

Scan to keep reading on your phone. No account needed to start.