This book examines the psychosocial, legal, and familial factors at play in the persistence in crime and social marginalization in adults with a history of juvenile delinquency, setting out the political and social implications, and delineating new lines of research. Presenting, for the first time, a summary of the main findings and conclusions of The Portuguese Study on Delinquency and Social Marginalization (PSDSM), this study addresses the following topics: the role of youth psychosocial factors on desistance from crime during adulthood in individuals with a history of juvenile delinquency; the relationship between serious adverse childhood experiences (e.g., having lived with a person with mental illness, physical abuse, emotional neglect) and juvenile justice involvement, persistence in crime, and psychosocial problems; the mechanisms involved in the link between serious childhood adversity and delinquency; the role of the juvenile justice system on psychosocial problems and persistence in crime during young adulthood; and finally the relation between adult psychosocial problems and criminal indicators in individuals with official record of juvenile criminal offenses. Findings from PSDSM have resulted in an extensive list of political and social recommendations for child protection services, justice system, mental health services, schools and universities. This timely title explores these findings and recommendations.