Genetics of co-developing conduct and emotional problems during childhood and adolescence

Common genetic influences offer a partial explanation for comorbidity between different psychiatric disorders1–3. However, the genetics underlying co-development – the cross-domain co-occurrence of patterns of change over time – of psychiatric symptoms during childhood and adolescence has not been well explored. Here, we show genetic influence on joint symptom trajectories of parent-reported conduct and emotional problems (overall N = 15,082) across development (4-16 years) using both twin- and genome-wide polygenic score analyses (genotyped N = 2,610). Specifically, we found 7 joint symptom trajectories, including two characterised, respectively, by jointly stable and jointly increasing symptoms of conduct and emotional problems (7.3% of the sample, collectively). Twin modelling analyses revealed substantial genetic influence on trajectories (h2 estimates range: .41-.78). Furthermore, individuals’ risk of being classified in the most symptomatic trajectory classes was significantly predicted by polygenic scores for years-of-education-associated alleles and depressive symptoms-associated alleles. Complementary analyses of child self-reported symptoms across late childhood and early adolescence yielded broadly similar results. Taken together, our results indicate that genetic factors are involved in the co-development of conduct and emotional problems across childhood and adolescence, and that individuals with co-developing symptoms across multiple domains may represent a clinical sub-group characterised by increased levels of genetic risk.