WEDNESDAY, Sept. 26, 2001 (HealthDayNews) -- If you're depressed and can't quit smoking -- or depressed because you just quit -- it may be because cigarette smoke is acting a lot like an antidepressant drug in your brain, says a new study.
"There's a high incidence of smoking among people who are depressed," explains Gregory Ordway, a professor of psychiatry at the University of Mississippi Medical Center in Jackson. "We also know that people who are depressed have a very difficult time quitting smoking, and often people who quit smoking suffer some depressive symptoms. So we hypothesized that smoking may produce some sort of antidepressant effect."
Ordway says chemicals in cigarette smoke mimic the effects of drugs that produce antidepressant effects in animals. But make no mistake, cigarettes are not antidepressant drugs, he adds.
"There's no Prozac-like chemical in cigarette smoke because Prozac is a selective serotonin reuptake inhibitor [SSRI]," Ordway says. An SSRI elevates levels of naturally occurring, mood-enhancing brain chemicals. "But there is something in cigarette smoke that inhibits another class of chemicals called monoamine oxidase inhibitors (MAOIs)." Drugs that inhibit MAOIs are antidepressants; they keep noradrenaline from breaking down in the system, thereby keeping one's mood higher, he says.
According to the National Mental Health Association, the symptoms of depression are caused by chemical imbalances in the brain and other parts of the body that control mood, sleep and how much energy we have. Antidepressant drugs act on the chemical pathways of the brain in order to correct these chemical imbalances. The association estimates about 18.8 million Americans age 18 and older suffer from some sort of depressive disorder.
To test his antidepressant theory, Ordway and his colleagues looked at a part of the brain linked to depression. They biopsied the locus coeruleus (LC) from seven cadavers of heavy smokers and compared the tissue with the locus coeruleus from nine cadavers from healthy nonsmokers. None of the people had been diagnosed with depression.
"The locus is a fairly primitive part of the brain, and yet it globally regulates neuronal function in a wide variety of brain regions, including those that are responsible for emotion," Ordway explains. The LC is located in the brain stem.
"We looked at several different proteins in the LC, and what we found in our comparison were chemical differences that can be produced in animals by repeatedly treating them with antidepressant drugs," Ordway says. Specifically, the brains of long-time smokers had much less of two proteins that are found at high levels in people who are seriously depressed or commit suicide. The findings are in the September Archives of General Psychiatry.
"This is the first demonstration that chronic cigarette smoking can produce changes in the brain similar to some, but not all, the changes we see in animals' brains and mimic at least some of the effects of antidepressants," Ordway says. "This study also increases the evidence that including antidepressant therapy in smoking cessation programs could be effective."
"This study is adding to the evidence that people who smoke are self-medicating their psychological or psychiatric symptoms of depression," says Dr. Karen Lasser, a research fellow at Harvard Medical School in Boston, Mass. "We published a study about a year ago, which showed very high rates of smoking in people with mental illness."
What To Do
Don't start smoking if you're trying to lift your mood, Lasser says. "We have plenty of antidepressant medications that do not cause cancer, and that's what we should be concentrating on."
For more on cigarettes and depression, see the American Psychological Association. And for more on depression, check out the National Institute of Mental Health.
