New research has uncovered a possible link between depression brought on by stress and adult-onset asthma in African-American women.
“The hypothesized mechanism linking depressive symptoms to asthma incidence is stress and its physiological consequences—particularly, effects on the immune system and the airways,” says study lead author Patricia Coogan, a research professor of epidemiology at Boston University.
“Psychological stress can bias the immune system to responses that might contribute to asthma.”
For the new study, published online in the journal Annals of Allergy, Asthma & Immunology, researchers followed nearly 32,000 African American women between 1999 and 2011 who participated in the long-running Black Women’s Health Study and completed health questionnaires every two years. The researchers rated the frequency with which women experienced 20 depressive symptoms.
Responses such as “I felt depressed,” “I felt lonely,” or “I could not get going” were summed into a scale ranging from zero (rarely or never experiencing depressive symptoms) to 60 (experiencing all depressive symptoms most or all of the time). The scale is commonly used in epidemiologic studies, with a score of 16 or higher used to identify individuals at high risk for depression.
As the frequency of depressive symptoms increased, the incidence of adult-onset asthma also rose—up to a twofold increase in women in the highest category of the depressive symptom scale. The incidence of asthma increased 2.8 times in women who had a symptom score of 16 or higher and who also reported use of antidepressants, a group at higher likelihood of suffering from depression.
The results are consistent with findings from several previous studies of depression and asthma incidence conducted in smaller and primarily white populations, Coogan says. But, she adds, “I was surprised at the magnitude of the relative risk in our highest category of depressive symptoms.”
According to the investigators, 11.6 percent of black women currently have asthma, and 13.1 percent have a lifetime prevalence of major depressive disorder. When the conditions occur concurrently, both are usually more severe.
Unlike children who experience intermittent asthma symptoms in response to allergy triggers or respiratory infections, adults with newly diagnosed asthma generally have persistent symptoms. Daily medications may be required to keep asthma under control. The condition can be fatal if not properly treated.
About half of adults who have asthma also have allergies. In some cases, adult-onset asthma may be the result of exposure to substances in work or home environments, with symptoms coming on suddenly.
While the new research does not establish a causal relationship between depression and asthma, it does suggest that depressive symptoms can precede asthma—instead of the other way around. The research team ascertained participants’ depressive symptoms before the women developed asthma. Women who reported childhood asthma were excluded from the study.
Stress a known trigger
Stress is a known trigger of asthma exacerbation in patients with the condition, the researchers say. A major depressive disorder may lead to overproduction of a corticotropin-releasing hormone and hyperactivity of the hypothalamic-pituitary-adrenal axis—hallmarks of stress.
“This is very early in this research, and speculative,” Coogan says. “What we can state with certainty now is that there is an association” between depressive symptoms and the onset of adult asthma.
“Given the high prevalence of both asthma and depression in women, the association is of public health importance.”
The researchers recommend additional studies exploring the mechanisms by which stress increases asthma risk, in hopes that subgroups at high risk might be identified, generating new therapies for prevention.
Poverty and asthma
There is a slightly stronger association between depressive symptoms and asthma onset in current and former smokers than in nonsmokers and in women age 40 and older.
In previous research, the Slone team showed that experiences of racism or childhood abuse, or having a high body mass index, also are associated with increased incidence of adult-onset asthma. In the case of racism or abuse, those stressful experiences may “get into the body somehow,” altering the immune system, Coogan says. And obesity can impact airways and lung function.
While there has been extensive research on childhood asthma, less is known about adult-onset asthma. The next phase of this research is looking into other psychosocial factors in adult asthma, by gauging whether women in economically disadvantaged neighborhoods have higher rates of developing the condition.
The National Institutes of Health and the National Cancer Institute funded the study.
Source: Boston University