To the Editor: Longitudinal research suggests that 30% to 50% of children with attention deficit hyperactivity disorder (ADHD) still meet the criteria for this diagnosis in young adulthood (1). Longitudinal research also suggests that children with ADHD are at a greater risk than normal subjects of arrest and imprisonment during early adulthood (2). However, to date and to our knowledge, no study has looked at the rates of ADHD in the adult prison population to assess whether this higher risk translates into a higher prevalence of prisoners with ADHD.

We examined a randomly selected group of patients referred to the psychiatry clinic in Mountjoy Prison for adult male offenders over a 10-month period to see how many met the DSM-IV criteria for ADHD. The psychiatry clinic is well placed to examine the rate of ADHD: although many prisoners are referred with psychopathology, 62% of the prisoners referred during the capture phase were sent to the clinic for personal problems or insomnia. Most prisoners in Mountjoy Prison are in their 20s or 30s. Fifty-five prisoners were assessed. Their mean age was 26.2 years. Five (9.1%) met the DSM-IV criteria for current ADHD.

The prevalence of ADHD among school-age children is estimated at 3% to 5% (DSM-IV). Accepting that 50% of these children have an illness that persists into young adulthood suggests that a randomly selected group of young adults should yield a prevalence rate of approximately 2.5%. This cross-sectional study suggests, therefore, that there is a higher-than-expected prevalence of ADHD among young adult prisoners, corroborating the higher risk of imprisonment found in longitudinal follow-up studies of children with ADHD and suggesting that ADHD is a diagnosis that should be borne in mind in adult forensic psychiatry.