Abstract
There is no single cause of NSSI in youth that reliably determines whether a child or adolescent will ultimately engage in these behaviors. Psychiatric problems and disorders often result from complex interactions of genetic predispositions, environmental events/stressors, and individual vulnerabilities, and the causes of NSSI are no different. This chapter begins with a review of several explanatory models for NSSI in youth, with a particular emphasis on the environmental/functional model, as this approach has the most support in the professional literature. Following this discussion, a comprehensive biopsychosocial framework developed by Walsh (2006) for understanding the causal variables contributing to the development of NSSI will be described. This framework leads directly to many of the recommended assessment and treatment techniques described in subsequent chapters.