One-year population prevalence estimates range from 2% to more than 10%, with a median of 4%. The prevalence of conduct disorder appears to be fairly consistent across various countries that differ in race and ethnicity. Prevalence rates rise from childhood to adoles- cence and are higher among males than among females. Few children with impairing con- duct disorder receive treatment.
The onset of conduct disorder may occur as early as the preschool years, but the first sig- nificant symptoms usually emerge during the period from middle childhood through middle adolescence. Oppositional defiant disorder is a common precursor to the child- hood-onset type of conduct disorder. Conduct disorder may be diagnosed in adults, how- ever, symptoms of conduct disorder usually emerge in childhood or adolescence, and onset is rare after age 16 years. The course of conduct disorder after onset is variable. In a majority of individuals, the disorder remits by adulthood. Many individuals with conduct disorder—particularly those with adolescent-onset type and those with few and milder symptoms—achieve adequate social and occupational adjustment as adults. However, the early-onset type predicts a worse prognosis and an increased risk of criminal behavior, conduct disorder, and substance-related disorders in adulthood. Individuals with conduct disorder are at risk for later mood disorders, anxiety disorders, posttraumatic stress dis- order, impulse—control disorders, psychotic disorders, somatic symptom disorders, and substance-related disorders as adults.
Symptoms of the disorder vary with age as the individual develops increased physical strength, cognitive abilities, and sexual maturity. Symptom behaviors that emerge first tend to be less serious (e.g., lying, shoplifting), whereas conduct problems that emerge last tend to be more severe (e.g., rape, theft while confronting a victim). However, there are wide differences among individuals, with some engaging in the more damaging behaviors at an early age (which is predictive of a worse prognosis). When individuals with conduct disorder reach adulthood, symptoms of aggression, property destruction, deceitfulness, and rule violation, including Violence against co-workers, partners, and children, may be ex- hibited in the workplace and the home, such that antisocial personality disorder may be considered.
Temperamental. Temperamental risk factors include a difficult undercontrolled infant temperament and lower-than-average intelligence, particularly with regard to verbal IQ.
Environmental. Family-level risk factors include parental rejection and neglect, inconsis— tent child-rearing practices, harsh discipline, physical or sexual abuse, lack of supervision, early institutional living, frequent changes of caregivers, large family size, parental criminal- ity, and certain kinds of familial psychopathology (e.g., substance-related disorders). Com— munity-level risk factors include peer rejection, association with a delinquent peer group, and neighborhood exposure to violence. Both types of risk factors tend to be more common and severe among individuals with the childhood-onset subtype of conduct disorder.
474 Disruptive, Impulse-Control, and Conduct Disorders
Genetic and physiological. Conduct disorder is inﬂuenced by both genetic and envi- ronmental factors. The risk is increased in children with a biological or adoptive parent or a sibling with conduct disorder. The disorder also appears to be more common in children of biological parents with severe alcohol use disorder, depressive and bipolar disorders, or schizophrenia or biological parents who have a history of ADHD or conduct disorder.