Suicide risk among patients using anti-smoking drugs did not increase when compared to those using nicotine patches and gum, according to a new study conducted by researchers from University of Bristol.

Varenicline (brand name Champix in the UK, Chantix in the US) is extensively prescribed world-wide to patients seeking to quit smoking. Varenicline and bupropion (brand name Zyban), the other main non-nicotine smoking cessation product, work by reducing nicotine cravings and withdrawal symptoms.

This finding certainly lessens safety concerns surrounding the drugs. Questions regarding the drugs were raised after patients reported depression, suicidal thoughts and anxiety.

This has led to the several safety warnings by regulatory agencies including the UK Medicines and Healthcare Products Regulatory Agency and the US Food and Drug Administration.

In order to test the theory, the Bristol researchers decided to study whether patients using Varenicline and bupropion were at an increased risk of suicide, self-harm and depression in comparison to those who were given nicotine replacement therapy products such as patches and gum.

They examined the medical records of 119,546 adults who were prescribed a smoking cessation product between September  2006 and October  2011. By using linked data from the Office for National Statistics mortality data and hospital episode statistics, the team looked into the rate of treated depression, self-harm and suicide in 31,260 (26 percent) patients prescribed varenicline, 6,741 (5 percent) patients prescribed bupropion and compared it with 81,545 (68 percent) people given nicotine replacement therapies.

After using three different analytical methods, the researchers found no evidence of an increased risk of treated depression or suicidal behaviour in patients using varenicline or bupropion when compared to those associated with nicotine replacement therapies.

"Given the concerns and accompanying safety warnings for these drugs, these findings are reassuring for users and prescribers of smoking cessation medicines," Dr Kyla Thomas, one of the study's lead authors, said in an official statement.

"These findings support those of our earlier study in a larger, more comprehensive assessment of this important issue," Co-author Professor David Gunnell said. "They will be of interest to patients, prescribers and drug regulators."