Although Champix (varenicline) and Zyban (bupropion) have been prescribed for over a decade in Great Britain, both drugs have been linked to reports of suicides, depression, and even murder. But a major study conducted by the Universities of Edinburgh and Dusseldorf tracked the health of 150,000 smokers prescribed the drugs and found no evidence of increased risk.

Current advice about both drugs says those taking either drug should stop and contact their doctor if they develop depressed or suicidal feelings. In the United States, warnings have been placed on the drug, highlighting the dangers of depressive episodes and suicidal thoughts. But the new study appears to refute such claims.

"On the basis of our extensive analysis, we believe it is highly unlikely that varenicline has any significant adverse effects on cardiac or mental health," said Professor Aziz Sheikh, co-director of the University of Edinburgh's Centre for Medical Informatics. "Regulators such as the United States Food and Drug Administration should review its safety warning in relation to varenicline as this may be unnecessarily limiting access to this effective smoking cessation aid."

The study found those taking Champix (called Chantix in the United States) and Zyban were no more likely to suffer depression or self-harm than those using nicotine replacement therapy. Additional research in Great Britain has found that Champix is the most effective stop-smoking aid, with more than 60% of those using it reporting that they have successfully quit. Although not as popular, Zyban is effective as well.

"Smokers typically lose three months of life expectancy for every year of continued smoking. Our research supports the use of varenicline as an effective and safe tool to help people quit," said Professor Daniel Kotz.

Researchers at Maastricht University, University College London, and Harvard Medical School also contributed to the study published in The Lancet Respiratory Medicine. The study hopes to remove any unnecessary stigma from the anti-smoking drugs.