Adolescents and adults with untreated attention deficit hyperactivity disorder (ADHD) are more vulnerable to developing substance use disorder (SUD) than those without ADHD. There is a wide body of epidemiologic data indicating that the diagnoses of ADHD and substance abuse occur together more frequently than would be expected by chance alone. When the diagnosis of ADHD is comorbid with bipolar or conduct disorder, the risk of comorbid SUD increases considerably. Those with ADHD are at greater risk for earlier onset substance abuse and even a family history of ADHD is a risk factor for developing SUD. Adult ADHD seems to be related to a longer period of active substance abuse and a lower recovery rate. A 1995 study by Biederman et al found that 52% of adults with ADHD, versus 27% of controls, had met criteria for substance abuse at some point in their lives.