Background Exposure to parental mental ill-health and poverty may impact child health problems across the life course. Although both maternal and paternal caregiver mental health may be important, few studies have unpicked the complex interrelationships between these exposures and family poverty. We therefore assessed the lifecourse mental health and poverty trajectories of caregivers and their impacts on the health of the next generation at the point of transition to adulthood.

Methods We used longitudinal data from the nationally representative UK Millennium Cohort study on 10500 children born between 2000 and 2002, followed through seven survey waves. Trajectories of poverty, caregiver and partner mental health were constructed from child age 9 months through to 14 years, adjusting for lone parenthood status. We assessed associations of these trajectories with socioemotional behavioural problems, cognitive disability and mental health problems at age 17 years using multivariable logistic regression whilst adjusting for confounders.

Results We identified five distinct trajectories: low poverty and good parental mental health (47%), persistent poor caregiver mental health (11%), persistent poor partner mental health (9%), persistent poverty (22%), and persistent poverty and poor parental mental health (11%). Compared with children exposed to low poverty and good parental mental health, those who experienced the combination of poverty, poor caregiver and partner mental health were at increased risk of socioemotional behavioural problems (adjusted odds ratio 4·2; 95% CI 2·7 – 6·7), mental health problems (aOR 2·5; CI 1·6 – 3·9) and cognitive disability (aOR 1·7; CI 1·1 – 2·5) at age 17. The associations were of similar magnitude when comparing the analyses by caregiver and partner status.

Conclusion Both caregiver and partner mental health co-occur with family poverty with more than 50% of children in the UK exposed to some degree of poverty and/or parental mental health problems. The combination of these exposures is strongly associated with adverse mental and behavioural health outcomes in the next generation, and requires public health attention.