CD refers to a repetitive and persistent pattern of antisocial behaviour (e.g., severe aggression to people or animals, deceitfulness or theft) by which the basic rights of others or major age-appropriate rules are seriously violated. With 5% of children and young people aged 5 to 15 years meeting ICD-10 criteria with a strict impairment requirement [31], CD is one of the most common mental health disorders of childhood and adolescence globally, and is a major reason for referral to child and adolescent mental health services in European countries.

Prevalence rates vary according to age, gender, socioeconomic status and degree of urbanity [32]. The gender ratio for CD is approximately 2.5, with males being overrepresented; males further exceed females in the frequency and severity of behaviours [33]. CD is more prevalent among youths from families of low socioeconomic status and in neighbourhoods characterized by high crime rates and social disorganization [31].

The disorder places large personal and economic burden on individuals and society, including the family, schools, police and criminal justice agencies. Large follow-up studies show poor adult outcomes for a high proportion of children and adolescents with CD in domains of violence, mental health, criminal activity, substance abuse and dependence, work and family life [34] [35].

The most antisocial 5% of children aged 7 years are 500 to 1000 times more likely than population children to display indices of serious life failure at age 25 years, such as drug dependency, criminality, unwanted teenage pregnancy, leaving school with no qualifications, and unemployment [36]. Large meta-analyses show that about half of imprisoned adolescent offenders has a diagnosis of of CD [26] [27].

Follow-back studies show that most (if not all) adults with antisocial personality disorder had prior CD [37]. About 90% of severe, recurrent adolescent offenders showed marked antisocial behaviour in early childhood. Importantly, early onset of CD is a strong predictor of persistence throughout childhood [38].