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FRIDAY, Oct. 2 (HealthDay News) -- The smoking cessation drug varenicline (Chantix) does not increase the risk for self-harm or depression, according to a new British study.

In July, the U.S. Food and Drug Administration mandated that the drug carry a "black-box warning" on its packaging, indicating that people who use it face increased risk for "serious neuropsychiatric symptoms," including changes in behavior, hostility, agitation, depressed mood, suicidal thoughts and behavior and attempted suicide.

In the new study, British researchers analyzed database information on 80,660 men and women, ages 18 to 95, who were prescribed a smoking cessation product between September 2006 and May 2008. Prescriptions were for varenicline, the antidepressant bupropion (Zyban) or nicotine replacement products, such as a patch, inhaler, gum, tablet or lozenge. People were followed through the period of the prescription and for three months after the date of their last prescription.

No clear evidence emerged that varenicline or bupropion increased the risk for self-harm, suicidal thoughts or depression, the study reported.

However, the researchers added that "the limited power of the study means we cannot rule out either a halving or a twofold increased risk."

They recommended further study of varenicline's effect on suicide risk. They also said that any risks associated with varenicline must be balanced against the long-term health benefits of stopping smoking and the drug's effectiveness as a smoking cessation product.

The study, which had no drug company funding, was published online Oct. 1 in BMJ.

More information

The Tobacco Control Research Branch of the U.S. National Cancer Institute has more on quitting smoking.