It's well-documented that young people diagnosed with Attention Deficit Hyperactivity Disorder are more likely to pick up cigarette smoking, start earlier when they do and become more seriously addicted to tobacco than peers without the disorder.
Yet a new analysis that pools data from more than a dozen published studies finds that adolescents who are prescribed stimulant medications to treat ADHD are less likely to smoke than those with ADHD who are not treated with the drugs.
Those medications include both amphetamine-based (Adderall and Vyvanse) and methylphenidate-based ( Ritalin and Concerta) drugs.
The findings are important given concerns raised about the long-term impact of stimulant treatment on substance abuse in general and cigarette smoking in particular, says clinical psychologist Scott Kollins, director of the Duke University Medical Center ADHD Program and senior author of the study published online today by the journal Pediatrics.
"We cannot draw any causal conclusions, but at the very least, we can be pretty confident when we talk to parents that this is not going to increase your kids' chance of smoking, and that's important," says Kollins, a professor in the department of psychiatry and behavioral sciences.
ADHD "can be very much in flux" around the pre-teen and teen years when smoking experimentation typically begins, says ADHD researcher Paul Hammerness, an assistant professor of psychiatry at Harvard Medical School, who was not involved in the new study. As teens with ADHD face increasing academic and social-emotional demands, they may turn to smoking to improve focus or reduce restlessness, or "as an example of being impulsive," he says. "This is often a tenuous development period."
Evidence on whether stimulant drugs influence smoking behavior has been mixed, with a 2013 meta-analysis combining five longitudinal studies finding no significant relationship between stimulant treatment and nicotine dependence.
For the new meta-analysis, Kollins and colleagues combined data from 14 published studies involving 2,360 participants (1,424 were treated with medication; 936 were not).
Although their findings were consistent with the 2013 analysis when focused solely on studies involving nicotine dependence, they differed when studies involving a broader range of smoking habits, such as occasional tobacco use, were included.
Overall, stimulant treatment was associated with a lower risk for subsequent smoking, and the protective effect was more pronounced in adolescence than in adulthood, in girls than in boys, and in studies in which participants got consistent treatment that was followed by medical providers.
"The message is not just that treatment is effective in reducing this risk, but that well-managed and consistent treatment over time is really what's associated with a lower risk," Kollins says.
The study results "don't really say anything about those kids who might not actually meet the criteria for ADHD, but who might be getting stimulant medication," he adds.
Part of the controversy surrounding the over-diagnosis of the condition and inappropriate use of stimulant drugs stems from the fact "that there are lots and lots of kids out there who have a diagnosis of ADHD, but in fact have not had a good, thorough assessment and probably don't meet the full criteria," he says.
Researcher Steve Lee, an associate professor of psychology at UCLA and lead author of the 2013 meta-analysis agrees: "I have little doubt that stimulant medication is being prescribed without careful diagnostic procedures and that's a significant problem."
"But it's also the case that in some communities children, and probably some adults, who could respond therapeutically and safely are being underprescribed and not getting the treatment they need," he says.