Background It is important to identify and provide preventative interventions for youth who are most at risk for offending behaviour, but the connection between early childhood or adolescent experiences and later delinquency adjudication is complicated. Aim To test for associations between specified mental disorders or maltreatment and later delinquency adjudication. Method Participants were a random sample of youth before the juvenile courts in two Northeast Ohio counties in the USA (n = 555) over a 4-year time frame (2003 to 2006). Results Logistic regression analysis identified a lifetime diagnosis of depression and/or bipolar disorder to be predictive of later youth delinquency adjudication, but found that childhood maltreatment (or involvement with the child welfare system) made delinquency outcomes less likely. Implications Study implications are discussed as they relate to professionals working in the fields of child welfare, social work, mental health and juvenile justice. Awareness of risks associated with maltreatment may have led to effective interventions, while there may be less awareness of risks from depression in young people; however, studies tend not to take account of intervention variables.