Conduct disordered adolescents hospitalised 1963-1990. Secular trends in criminal activity.

Secular trends in the criminal activity of conduct disordered adolescents admitted as psychiatric in-patients in Norway were examined. A nationwide sample of 650 adolescents hospitalised with DSM-IV Conduct Disorder during the years 1963-1990 was followed up 12-33 years after index hospitalisation by register linkage to the National Crime Register. In all, 469 patients, 82% of the males and 57% of the females, had a criminal record at follow-up. The study population was divided into four consecutive cohorts and gender-specific cohort differences in registered criminality were investigated, using survival analysis. There was a marked increase and subsequent levelling off in overall registered criminality from the first to the most recent cohort of conduct disordered females, in contrast to unchanged crime rates in conduct disordered males. Monitoring specific types of crime, males' violent crime rates initially increased but levelled off in more recent cohorts, whereas female violent crime rates increased steadily, with the highest level seen in the most recent cohort. A marked increase in drug offences was observed in both genders. Cox regression demonstrated numerous strong cohort effects, even when controlling for other important factors, including substance use comorbidity. Research into causal mechanisms is warranted.