toledoblade.com --

An unsettling new explanation for the strange link between cigarette smoking and mental illness has quietly emerged from research done during the last few years.

Experts long have known that psychological disorders are unusually common among cigarette smokers.

One 2000 Harvard University study, for instance, concluded that almost half of all cigarette smokers in the United States have some form of mental illness.

The researchers found that many smokers have symptoms that fit neatly into the standard psychiatric definitions of major depression, anxiety disorder, phobias, alcohol or other drug dependence, and antisocial personality.

Other studies show that almost 90 percent of people with the most serious mental disorders, such as schizophrenia, smoke cigarettes. Individuals with mental illness also are among the heaviest smokers.

So what started first? The illness or the smoking?

Mental illness occurs first, according to the time-honored theory. People with mental illness start smoking, and smoke more, because nicotine relieves their symptoms and makes them feel better. In addition, they may be more psychologically vulnerable to nicotine addiction or the allure of tobacco advertising.

New studies, however, suggest that cigarette smoking is the cause - not the consequence - of some psychiatric disorders, including common conditions that involve depression and anxiety.

Tons of scientific evidence over the last 60 years have unmasked tobacco's role in heart attacks, lung cancer, and other physical diseases. Cigarette smoking causes more than 430,000 deaths annually, according to the U. S. Centers for Disease Control and Prevention. That's 1 in every 5 deaths.

Suspicion that tobacco may cause mental illness arose in the 1990s. It still gets little attention, compared to tobacco's effects on physical health.

Some of the first hints emerged from a 1998 study on teenage smokers headed by Dr. Naomi Breslau, a psychiatrist at the Henry Ford Health Systems in Detroit.

Her five-year study of 1,000 young adults found that smoking increased the risk for developing depression. People who smoked before the study began had twice the risk of developing major depression during the following five years as nonsmokers.

Larger studies have bolstered the link.

A University of Cincinnati study of 8,704 teenagers, for instance, found that mentally healthy teenagers who start smoking are four times more likely to develop depression than their nonsmoking peers.

Harvard University researchers studied cigarette smoking and mental health in 4,500 adolescents and adults. Mentally healthy teenagers who smoked at least one pack a day faced a 16-fold greater risk of developing panic attacks, a seven-fold risk of developing serious phobias, and five times the risk of anxiety attacks than peers who smoked less than one pack.

How could cigarette smoking cause mental illness?

Experts don't know.

Some suspect that the nicotine and other chemicals in cigarette smoke may damage or change the normal activity of brain cells.

Others think that nicotine and high levels of carbon monoxide in cigarette smoke work together to cause symptoms of psychological illness.

Nicotine's stimulant action keeps smokers in a state of heightened alertness. With minds racing, hearts pounding, and blood pressure up, they are more likely to overreact to body sensations and situations in the environment.

Carbon monoxide may cause breathing disorders responsible for one sensation - a false sense of suffocation - that triggers many panic and anxiety attacks. One attack then engenders fear of others, and causes changes in behavior.

People should know about the findings, even though many questions remain unanswered.

It may make young people think twice about that first cigarette, for instance. And it could make confirmed smokers with diagnosed psychological problems wonder if quitting will ease their symptoms.

Michael Woods is the Blade's science editor. His column on health appears each Monday. Email him at mwoods@theblade.com.

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