Harmonized psychiatric diagnosis data from the Adolescent Brain Cognitive Development Study.

In the Adolescent Brain Cognitive Development (ABCD) Study, the computerized Kiddie Schedule for Affective Disorders and Schizophrenia (KSADS-COMP) was administered to 11,858 participants at up to eight waves. The structure of these data creates the need for many scoring decisions. Present and lifetime diagnoses, and parent and youth reports, are each stored separately; two instrument versions are pooled into shared columns; the same administrative codes represent several distinct forms of missingness; branch-skip logic produces missing data by design, and modules were added and dropped across the biennial schedule. Researchers resolve these features differently, so definitions of diagnoses vary significantly across studies. The consequences are substantial: holding the data fixed at release 7.0, the prevalence of any single disorder in ABCD ranges from 1.9% to 56.8%, depending on which definition is used. In this paper, we present a pipeline that makes each of these decisions explicit, along with a harmonized, analysis-ready diagnostic dataset for ABCD release 7.0. We also provide recommendations for multiverse analysis and a clinically informed recommended configuration.