Smoking cessation drugs may not increase depression risk

Contrary to the popular notion, smoking cessation drugs may not increase the risk of serious neuropsychiatric effects such as depression, hostility or suicidal behaviour, a new global study has found.

Compared to the nicotine patch and a placebo, the smoking cessation drugs varenicline and bupropion do not show a significant increase in neuropsychiatric adverse events, researchers said.

"There are 1 billion smokers in the world and nearly 6 million smoking-related deaths each year, but there are only three approved medication treatments for quitting - nicotine replacement therapies like the patch and the two non-nicotine medications, bupropion and varenicline," said Robert Anthenelli from University of California.

It is the result of a Food and Drug Administration (FDA) mandate following post-marketing reports suggesting varenicline and bupropion might cause adverse neuropsychiatric events, such as increased agitation, depression, hostility or suicidal behavior.

The study is important because it prospectively examined the neuropsychiatric safety risks and quit-enhancing potential of the three medication classes versus placebo in a rigorous, adequately-sized, randomised controlled trial, Anthenelli said.

Researchers sought to directly assess the safety and efficacy of varenicline and bupropion compared to the nicotine patch and to a placebo in smokers with and without psychiatric disorders.

It involved a randomised, controlled, double-blind trial examining more than 8,000 smokers seeking to quit in 16 countries over a period from November 2011 to January 2015.

Trial participants, investigators and research personnel were blinded to who received which treatment.

"This is the first study to compare the safety and efficacy of the three first-line smoking cessation aids on the market, head-to-head, in smokers. It is the largest double-blind smoking cessation medication trial to date," said Anthenelli.

In terms of safety, approximately 2 per cent of non-psychiatric participants reported moderate or severe adverse neuropsychiatric events for any of the treatments, researchers said.

Specifically, it was 1.3 per cent for varenicline, 2.2 per cent for bupropion, 2.5 per cent for the nicotine patch and 2.4 per cent for placebo.

In the cohort of participants with psychiatric disorders, moderate and severe adverse neuropsychiatric events were slightly higher across the board - 6.5 per cent for varenicline, 6.7 per cent for bupropion, 5.3 per cent for the nicotine patch and 4.9 per cent for placebo.

Anthenelli said the risk difference in the incidence of serious neuropsychiatric adverse events for varenicline and bupropion was not significantly higher than placebo - but that psychiatric patients trying to stop smoking are likely to have more confounding factors in treatment and appear to have a harder time quitting.

The findings were published in the journal The Lancet.