Involvement with illicit drugs among young people has been explained by a risk-factor matrix. This study aims to compare childhood psychopathology as a predictor between self-reported illicit drug use without registered drug offending and police informed drug offending among males in a prospective birth cohort study.

A general population sample of 2946 8-year-old Finnish boys was followed up from age 8 to 18. In 1989, childhood psychopathology was assessed using the Rutter scale and Child Depression inventory. Information about self-reported drug use at age 18 or police-registered drug offending during years 16 to 20 years was collected from 79.3% (n=2336) of the subjects.

Childhood psychopathology predicted exclusively police registered drug offending. After adjusting for family background, both severe and moderate conduct problems and ADHD symptoms were associated with subsequent police-registered drug offence. Self-reported illicit drug use was predicted only by non-intact family structure.

Our results demonstrate a clear difference, occurring already in childhood, between young men with self reported illicit drug use and those with police registered drug offending. More severe illicit drug involvement, such as police-registered drug offending, is a continuum of a childhood externalizing problem behaviour, while self-reported occasional illicit drug use does not inevitably associate with psychopathological problems in childhood. Accordingly, the preventive needs and the age period for intervention may be dissimilar for young people with divergent involvement with illicit drugs.