Child maltreatment and age of alcohol and marijuana initiation in high-risk youth

•Longitudinal data were used to assess the impact of child maltreatment, and internalizing and externalizing behavior problems, on the initiation of alcohol and marijuana use among high-risk youth.•Externalizing problems at age 8 mediated the link between child maltreatment and both alcohol and marijuana use initiation.•There was a direct effect of physical abuse on alcohol use initiation, and mediated effects from sexual abuse and neglect through externalizing behaviors for alcohol and marijuana use.•Externalizing behaviors are one mechanistic pathway from early childhood to age of substance use initiation among maltreated youth.