Anti-depressants can almost double a smoker's chance of quitting compared to using nicotine patches alone, according to a study.

It found that of those who used an anti-depressant treatment, 30.3% stayed off cigarettes at least a year. This compares to 16.4% of those using patches and 15.6% of those who received a placebo.

The research was funded by Glaxo Wellcome, the company that manufactures bupropion, the anti-depressant used in the trial.

Eight of the 12 doctors involved in the study declared a link to the pharmaceuticals giant.

The research appears in the New England Journal of Medicine.

Breaking the habit

The US researchers said: "We found that treatment with bupropion alone or in combination with a nicotine patch resulted in higher long-term abstinence rates than did the use of placebo or a nicotine patch alone."

Abti-depressants could tackle the root causes of addiction

Earlier research had suggested that depression plays a role in smoking and that bupropion, along with other anti-depressants, could work as a cessation aid.

The researchers recruited 893 volunteers through advertisements in Arizona, California, Nebraska and Wisconsin.

They excluded anyone who had been diagnosed with clinical depression.

The patients were then allocated a therapy and given a target of eight days to quit. The therapy lasted for 17 weeks.

After 12 months, the researchers reviewed the volunteers' progress.

While the results are promising for prospective ex-smokers, there were side-effects:

• Insomnia - affected almost one-third of patch users and 42% of those taking bupropion compared to 20% of those on placebos;
• Dry mouth - twice as likely to be experienced by those on pills;
• Abnormal dreams - seven times as likely in patch users;
• Severe allergic reaction - suffered by three of the 487 bupropion recipients 14 to 20 days after starting therapy;
• Weight gain - slight, but similar, in all groups after seven weeks of treatment.

Combination hope

Each year two million of the UK's 12 million smokers take part in No Smoking Day, but only 40,000 manage to give up, according to Action on Smoking and Health.

However, ASH said the research supported other trials showing that therapies prove more effective when used in combination.

The campaign group said the research offers new hope to would-be ex-smokers.

A spokeswoman said: "This is interesting research that offers promising results.

"The main advantage of this approach is that it does not involve nicotine and is less likely to lead to dependence."

She added that there is strong and well-established link between smoking and depression.

"Nicotine reacts with the pathways in the brain dealing with pleasure and reward," she said. "Perhaps anti-depressants work because they deal with the same parts."