Attention deficit hyperactivity disorder and severity of substance use: the role of comorbid psychopathology

Attention deficit hyperactivity disorder (ADHD) is a highly comorbid disorder, and, as such, there is much confusion surrounding the exact role it plays in increasing susceptibility to harmful behaviors. To date, no studies have examined the impact of adult ADHD on severity of substance use, while controlling for comorbid psychiatric disorders. Using a structured cross-sectional survey of 269 regular polysubstance users in Sydney, Australia, this study aimed to determine whether ADHD was a risk factor for more severity of substance use, and whether this effect remained when Borderline Personality Disorder (BPD) and Conduct Disorder (CD) diagnoses were controlled for. Rates of psychiatric disorders were high, with 45% meeting criteria for ADHD, 47% for BPD, and 64% for CD. While bivariate analyses showed that adult ADHD was significantly associated with all indicators of drug use severity, this effect did not remain once confounding factors were controlled. While ADHD accounted for very few differences in drug use severity, CD was found to independently predict all drug use severity indicators, including earlier onset, greater polydrug use, more frequent stimulant use, and greater risk for stimulant dependence. These results suggest that CD, rather than ADHD, is the strongest predictor of differences in patterns of drug use severity. The extensive comorbidity among this sample highlights the great potential for misattributing drug use risks to ADHD, and that it is important to account for psychiatric comorbidity to properly discern what underlying variables account for differences in harmful drug use behaviors.