Trajectories of conduct problems: exploring genetic and early-life risk factors and adult outcomes

Background: Conduct problems trajectory studies suggest their development is highly heterogeneous and that different trajectories may be uniquely associated with different risk factors and outcomes. Yet studies combining trajectory modelling and a varied set of genetic and early-life risk factors, as well as adult outcomes, are scarce. Methods: We analysed data from the Twins Early Development Study (TEDS), a longitudinal UK twin cohort (N=18,993). Conduct problems were measured using parent reports of the Strengths and Difficulties Questionnaire (SDQ) conduct problems subscale at four time points between ages 4 and 12. Trajectories were identified using growth mixture modelling. We then explored associations between trajectory class membership and genetic and early-life factors (age 4), and adult life and clinical outcomes (age 26). Results: Four conduct problem trajectories were identified: Low Stable (n=15,304, 81%), Childhood-Limited (n= 1,395, 7%), Childhood-Increasing (n=1,791, 9%) and Persistent (n=503, 3%). Associations with risk factors followed a stepped pattern with individuals in the Persistent class reporting higher genetic liability and early-life risk. Higher genetic vulnerability to attention-deficit hyperactivity disorder distinguished between the Low Stable and all other classes. Higher externalising problems polygenic score, negative family environment and hyperactivity/inattention, distinguished between all classes, except the Childhood-Increasing and the Childhood-Decreasing ones. Children experiencing conduct problems in childhood were at higher risk for reporting poorer current and lifetime mental and physical health outcomes, lower educational attainment and financial difficulties.Conclusions: Children experiencing conduct problems face multiple risk factors that should be addressed. Previously identified risk factors (i.e. negative family environment, hyperactivity/inattention), continued to differentiate between all classes after accounting for various psychiatric polygenic scores, validating existing interventions targeting these factors. Childhood conduct problems were associated with poor outcomes in adulthood, emphasising the need to develop interventions identifying those at risk early.