Nicotine may benefit some with mental illnesses.

Smoking may alleviate some of the cognitive deficits associated with certain mental disorders such as schizophrenia and attention-deficit hyperactivity disorder (ADHD), according to a review of studies published in the Journal of the American Medical Association (JAMA).

According to the article, "Link Between Smoking and Mental Illness May Lead to Treatments," about 41 percent of individuals who have had a mental disorder in the past month smoke, compared to 22.5 percent of those who have never had a mental illness. Attempts by the mentally ill to quit smoking not only incite nicotine withdrawal symptoms but also lead to the return of the cognitive deficits associated with their disorders.

In one study cited in the article, smoking was shown to enhance attention and working memory among 25 smokers with schizophrenia but not in another 25 without the illness. When the 50 smokers tried to quit, working memory was impaired in those with schizophrenia but not those in the control group.

Another study found that the thousands of chemicals contained in cigarettes appear to alter gene expression in all individuals but may actually work to "normalize" the expression of some genes in people with schizophrenia. The researchers drew this conclusion after examining postmortem brain tissue from the hippocampus of smokers with schizophrenia, nonsmokers with schizophrenia, and smokers and nonsmokers without a mental disorder.

The findings of these and other studies are prompting some researchers and pharmaceutical companies to study drugs that target nicotine receptors in the brain but lack the disadvantages associated with nicotine. Such drugs could improve the quality of life for individuals with schizophrenia and ADHD, though they would not cure the disorders.

For more information about the studies on nicotine and mental illness, see the February 1 issue of JAMA.