To estimate the prevalence of children in the Australian population with risk factors for adult mental illness.

Key risk factors and risk domains were identified from a 2013 review of longitudinal studies on child and adolescent determinants of adult mental illness. Data items were identified from the Longitudinal Study of Australian Children that map onto the risk domains and were used to estimate the prevalence of these key individual risk factors and the magnitude of multiple risk in children aged 3 months to 13 years.

Even by infancy, risk factors for adult mental illness are highly prevalent, with 51.7% of infants having multiple risks. In 10 infants, 1 was born to mothers who consumed daily alcohol and 1 in 8 to mothers who smoked cigarettes daily during pregnancy. Also, 10.5% of infants were in families where the parents had separated, which increased to 18% in 10–11 year-olds. Psychological problems in the clinical range (based on the Strengths and Difficulties Questionnaire total problems score) ranged from 7.8% to 9.7% across the 4–13 years age range. Risks from negative parenting behaviours were highly prevalent across age groups. Two-thirds of children aged 12–13 years had parents who displayed low warmth or exhibited high hostility/anger. Across childhood, one in seven children are in families exposed to 3+ major life stressors. By age 8–9 years, more than 18% of children are exposed to >=5 risk factors.

We find that modifiable risk factors for adult mental illness occur at the earliest stage in the life course and at greater prevalence than is commonly recognised. Considerable capacity will be required in child and adolescent mental health services and complementary family support programmes if risk factors for adult mental illness that are already apparent in infancy and childhood are to be addressed.