Smoking and Schizophrenia Linked by Alterations in Brain Nicotine Signals

Schizophrenia is associated with increased rates and intensity of tobacco smoking. A growing body of research suggests that the relationship between schizophrenia and smoking stems, in part, from an effort by patients to use nicotine to self-medicate symptoms and cognitive impairment associated with the disease.

A new study, published in the current issue of Biological Psychiatry, sheds light on this hypothesis. The authors 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 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.

Nicotine mimics the actions of a natural chemical messenger, acetylcholine, which stimulates the receptors for nicotine in the brain. So, to conduct this work, Yale University School of Medicine researchers used single photon emission computed tomography to quantify the availability of nicotinic acetylcholine receptors (β2*-nAChRs) in smoking and nonsmoking individuals with schizophrenia and healthy subjects.

First author and Assistant Professor Dr. Irina Esterlis details their findings, "We found a blunted effect of tobacco smoking on the β2*-nAChR system in individuals with schizophrenia. Furthermore, we found that lower receptor availability of β2*-nAChRs in smokers with schizophrenia is associated with worse negative symptoms and worse performance on tests of executive function."

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

Scientists have found that smoking and schizophrenia are tightly linked, but are not sure why. Could nicotine actually be helping the disorder? If so, then it is a double-edged sword, because smoking is a life-threatening behavior.

Now, new research on the effects of nicotine in people with schizophrenia is beginning to answer these questions and uncover clues that may help to treat this serious disorder. Schizophrenia is characterized by disordered thinking; hallucinations, such as hearing voices; and delusions, such as paranoid beliefs that people are conspiring against you.

Schizophrenia affects about 1 percent of the population and places a substantial burden on those afflicted, their families, and society.

Many people with schizophrenia smoke, and their unique smoking behaviors have led scientists to believe that nicotine, the addicting substance in tobacco, may represent a form of self-medication, normalizing some central nervous system deficits involved in the disorder.

People with schizophrenia smoke up to three times more than the general population and more than most psychiatric populations. Schizophrenia patients who smoke also have higher levels of nicotine in their bodies because they tend to extract more nicotine per cigarette than other smokers.