The Epigenetic Pathways to Conduct Problems Study consists of a subsample of youth (n = 339, 50% female) nested within a larger study of DNA methylation in ALSPAC (www.ariesepigenomics.org) who follow previously established conduct problem trajectories and have epigenetic data at two or more time points (birth, age 7, age 9). The trajectories have been identified and validated using General Mixture Model based on data drawn from the Strengths and Difficulties Questionnaire ‘Conduct Problem’ subscale (4–13 years; 18). The conduct problem trajectories are: (i) Low (25.4%), Childhood-limited (24.8%), (iii) Adolescent-onset (20.4%), and (iv) Early-onset persistent (29.5%). This subsample is comparable to the full trajectory sample (n = 7,218) in terms of environmental risk and psychiatric comorbidity (14). DNA methylation was available for 326 youth at birth, 332 at age 7, and 339 at age 9. Except for factor analyses, in which we used data from all youth, the present study only included youth following the early-onset, persistent conduct problem trajectory, who had complete data for CU and internalizing problems (total n = 84). Consistent with prior research (15), these youth
