Washington, Sep 17 (IANS): There is a close association between schizophrenia and increased rates of tobacco smoking. The relationship between them stems, in part, from an effort by patients to use nicotine to self-medicate symptoms and cognitive impairment associated with the disease, shows a new study.

Researchers at Yale University's school of medicine found that the level of nicotine receptors in the brain was lower in schizophrenia patients than in a matched healthy group. Further, smoking, which is known to increase the levels of receptors for nicotine in the brain, had this effect in both groups, although it was blunted in schizophrenia.

However, in the schizophrenia group, the smoking-related increase in the level of nicotine receptors was associated with lower levels of social withdrawal, blunted emotional and motivational responses, as well as better cognitive function, found the study.

Nicotine mimics the actions of a natural chemical messenger, acetylcholine, which stimulates the receptors for nicotine in the brain.

"We found that lower nicotinic-acetylcholine receptor availability in smokers with schizophrenia is associated with worse negative symptoms and worse performance on tests of executive function," explained Irina Esterlis, an assistant professor at Yale University.

These findings may be relevant to the high rates of smoking in schizophrenia.

"The data seem to suggest that smoking might produce some clinical benefits for some patients by increasing the availability of receptor targets for nicotine in the brain," noted John Krystal, editor of the journal Biological Psychiatry that published the study.

"These findings suggest that nicotinic-acetycholine receptors may be a target for developing treatments for negative symptoms and cognitive deficits associated with schizophrenia, for which no effective treatments exist," Krystal concluded.