The link between depression and smoking, long observed by health-care experts, is real and strong, a new government report shows.
People aged 20 and older with depression are twice as likely as others to be cigarette smokers, the researchers from the US Centres for Disease Control and Prevention found. And as the severity of depression increased, so did the number of smokers.
The magnitude of the link was surprising, said researcher Laura Pratt, an epidemiologist at the CDC's National Centre for Health Statistics, which published the findings April 14.
"The relationship between depression and smoking has been getting stronger over time," she said. Studies found only a small, insignificant link among Americans in 1952 and 1970, she said. But when Pratt and her co-researcher Debra Brody analysed information from 2005 to 2008 culled from the National Health and Nutrition Examination Survey, they found that:
About 43% of adults 20 and older who had depression smoked, compared with 22% of that age without depression.
Women with depression had similar smoking rates as men, although women without depression smoked less than men.
As depression worsened, the percentage of adults who were smokers increased.
Depressed smokers smoke more than smokers without depression.
Adults who are depressed and smoke are less likely to quit than are smokers who are not depressed.
About 7% of US adults aged 20 and older had depression in 2005 to 2008, the survey found. About half of those younger than 55 who had depression at the time of the survey were smokers, but less than a fourth of that age group without depression were smokers.
Since the US Surgeon General's report on the ill effects of smoking was issued in 1964, cigarette smoking among adults nationwide has been cut in half, but about 21% of adults overall still smoke, the report noted.
"Everyone knows people with depression are more likely to smoke," Pratt said, but what surprised her, she said, was the extent to which that was found true in the study.
For instance, among women aged 20 to 39 they found that 50% of those with depression smoke, whereas just 21% of those without depression do.
Smoking a form of 'self-medicating'
Even adults with mild depressive symptoms -- those who wouldn't qualify for a diagnosis of clinical depression -- were more likely to smoke than were people with no symptoms of depression, the researchers found.
Exactly why depressed people tend to smoke more was beyond the scope of the study, Pratt said, but some research has suggested they might be self-medicating, with the cigarettes somehow acting as a calming or relaxing mechanism.
Stanton A. Glantz, director of the Centre for Tobacco Control Research and Education at the University of California, San Francisco, said the findings were not surprising.
And he agrees that depressed people who smoke may be self-medicating. Part of the problem, he said, is that mental health professionals have been slow to deal with the tobacco issue.
"There's a myth that somehow if you deal with it, [by encouraging them to quit smoking,] it makes it harder to deal with underlying mental illness," Glantz said. "Just the opposite is true." - (HealthDay News, April 2010)