Familial risk for psychosis may interact with environmental risk factors.

We are studying a large birth cohort of children of mothers with psychotic disorders, themselves at high risk of developing a psychotic illness, to understand the developmental aetiology of psychotic illness.

Our aim is to examine whether exposure to environmental stressors in childhood, including timing of exposure, is a risk factor for psychotic illness, independent of familial liability. Specificity to maternal schizophrenia is explored.

We used record-linkage across state-wide registers (midwives, psychiatric, child protection and mortality, among others) to identify 15,486 offspring born in Western Australia 1980–2001 to mothers with a lifetime history of psychotic illness (case children) and compared them with 452,459 offspring born in the same period to mothers with no known psychiatric history (comparison children).

A total of 4.1% of case children had developed a psychotic illness compared to 1.1% of comparison children. Exposure to environmental risk factors including obstetric complications, aboriginality, lower socioeconomic status, discontinuity in parenting and childhood abuse significantly increased risk of psychotic illness in offspring. Length and age at time of discontinuity in parenting impacted on risk. At the same time, case children were also significantly more likely than comparison children to be at risk of experiencing these adverse life events.

Exposure to environmental stressors is associated with psychotic illness, and timing of exposure is important. However, children already at increased familial risk for psychotic illness are also at increased risk of experiencing these environmental stressors.

The authors have not supplied their declaration of competing interest.