Adolescents diagnosed with both attention-deficit/hyperactivity disorder and conduct disorder are three to five times more likely to smoke tobacco and drink alcohol, and to have begun doing so at an earlier age, than those with neither disorder, an analysis of data from the National Health and Nutrition Examination Survey shows.

The study of 2,517 participants aged 12-15 years found that those with ADHD alone were twice as likely to use tobacco than were controls but were not more likely to consume alcohol. Participants with a conduct disorder diagnosis alone did not have an increased likelihood of either behavior, wrote Dr. William B. Brinkman of the Cincinnati Children’s Hospital Medical Center and his colleagues (Drug Alcohol Depend. 2014 Dec. 16 [doi:10.1016/j.drugalcdep.2014.11.018]).

Inattentive “symptoms were significantly associated with use of both tobacco and alcohol: for every one symptom increase, the likelihood of tobacco and alcohol use increased by 10% and 8%, respectively, and the likelihood of initiating tobacco or alcohol use at a younger age increased by 8% for each,” Dr. Brinkman and his colleagues wrote.

They cited several limitations. For example, the National Health and Nutrition Examination Survey data were collected 10 years ago. Also, adolescents were asked about “ever” trying tobacco and alcohol, and that definition of use was quite broad. “Using narrower definitions (e.g., requiring frequent or daily use) might lead to different results, but we were unable to examine this due to small numbers of participants who met more stringent requirements,” they said. “Similarly, we were unable to assess the effects of other comorbidities (e.g., anxiety and depressive disorders) because there were not enough young adolescents with both the exposure and the outcome.”

Still, in light of these findings, prevention efforts aimed at promoting the reduction of ADHD and conduct disorder symptoms in the general population might ultimately help “reduce or delay onset of tobacco and alcohol use,” Dr. Brinkman and his associates suggested.

The study and some authors were supported by the National Institute of Mental Health. No conflicts of interest were declared.