Kids with ADHD who were treated with these so-called stimulant medications were about half as likely to smoke as children with this disorder who weren't treated with these medications, researchers found.
"We found an association between treatment with stimulant medications and a lower risk of smoking in adolescence and adulthood," said study researcher Erin Schoenfelder, clinical psychologist at Duke University School of Medicine in Durham, North Carolina.
About 11% of American children aged 4 to 17 have a diagnosis of ADHD, according to the US Centres for Disease Control and Prevention (CDC). Children with ADHD can be impulsive, have trouble concentrating and may have other behaviour problems. About 70% to 80% of children respond to stimulant medicine, according to the CDC. Behaviour therapy can also help.
Experts have long known that children with ADHD have a higher risk of starting to smoke cigarettes. Teens with ADHD are two to three times more likely to smoke cigarettes than their friends who don't have the diagnosis, according to Schoenfelder, citing previous research.
But, research on the effects of ADHD stimulant medicine on the risk of smoking has been conflicting.
To try to better answer the question of whether or not these medications could help prevent kids from smoking, the Duke researchers re-analysed the results of 14 studies of cigarette smoking and ADHD treatments. The studies included more than 2 300 children with ADHD. About 1 400 of the kids were being treated with stimulant medications, according to the new analysis.
The studies were published between 1980 and 2013. The average follow-up time was about seven years. The researchers compared the teens treated with stimulants to those who weren't to see which group was more likely to smoke.
Overall, those on medications were about half as likely to smoke as those not on the medications, Schoenfelder said.
"Those who took their medication consistently and for a longer period of time had an even lower risk of smoking," she added.
The data she analysed overwhelmingly showed that medications appear to decrease the risk of smoking, according to Schoenfelder.
Like all medications, ADHD medicines have side effects. This analysis showed a "slight effect" on growth, she said. However, that finding must be weighed against the many positive long-term benefits, she explained.
Schoenfelder pointed out that the researchers "can't say based on this study that the treatment caused the lower rate of smoking, but there is an association we found."
However, association does not prove a cause-and-effect relationship.
Kids try to self-medicate
One potential reason medication might have an effect is that both nicotine and the stimulant medications used to treat ADHD operate on the same pathways in the brain. They both improve the same processes that are disrupted in ADHD, according to Schoenfelder.
"Kids who have ADHD know that something is not quite right," said Dr Trevor Resnick, chief of the department of neurology at Miami Children's Hospital, who commented on the study.
"They try to self-medicate," he explained, and "cigarettes would be an example of self-medication." As a result, children with ADHD have a much higher risk in general of turning to cigarettes, pot or illicit drugs, he said.
"What this study shows, similar to previous research, is that successful treatment of ADHD with stimulant medication decreases the risk of self-medication in these children," Resnick noted.
While stimulant medications do have several possible side effects, Resnick said, "most kids are able to tolerate" the medication.
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