Table 1.
Prevalence of Self-Reported DSM–IV Symptoms of Externalizing Disorders and Rates of Substance Use in Longitudinal Twin Sample
| Behavioral measure | Age 12 years | Age 17 years |
|---|---|---|
| Externalizing disorders | ||
| Conduct disordera | 1.9% | 8.8% |
| ADHD–attentionb | 1.6% | 6.0% |
| ADHD–hyper/impulsiveb | 1.4% | 4.4% |
| Substance usec | ||
| Tobacco use | 5.4% | 20.3% |
| Alcohol use | 24.9% | 58.2% |
| Illicit drug use | 6.9% | 21.5% |
Note. DSM–IV = Diagnostic and Statistical Manual of Mental Disorders (4th ed.).
a
Three or more DSM–IV symptoms endorsed.
b
Six or more DSM–IV symptoms endorsed.
c
Age 12: use = any experimentation with substance; age 17: use = repeated use of substance.