The study, a national survey of more than 300,000 U.S. adults, shows that those reporting more days of poor mental health in the previous month were more likely to also report having asthma.
In the survey, which was conducted in 2006, participants were asked how many days during the past month they had poor mental health, including stress, depression, and emotional problems. They were also asked if a doctor, nurse, or other health care provider had ever diagnosed them with asthma, and if so, whether they still had asthma.
Compared with people who reported no days of poor mental health in the previous month, people reporting up to a week of poor mental health in the previous month were 38% more likely to say they currently had asthma.
By the same comparison, people reporting one to two weeks of poor mental health in the previous month were 49% more likely to report currently having asthma. People who reported two to three weeks of poor mental health in the previous month were 67% more likely to report currently having asthma, and people reporting three or more weeks of poor mental health in the previous month were more than twice as likely to report currently having asthma.
The researchers -- who included Thomas Chun, MD, of Brown University's medical school in Providence, R.I. -- considered participants' age, gender, race, smoking, marital status, obesity, exercise, overall health, and social class. But they didn't have data on other factors, such as a family history of asthma and allergies or whether participants had been born prematurely or had mothers who smoked.
Those findings, published in December's edition of Chest, don't prove that poor mental health causes asthma or vice versa. That's partly because participants weren't followed over time and also because the data were self-reported since participants' medical records weren't checked. Also, the study only looked at adults; it didn't include children with asthma.
But Chun's team notes that other observational studies have shown a possible link between mental health problems and asthma. The exact nature of that connection needs further study, Chun and colleagues conclude.