by Kim Krisberg

It’s often said that hard work never hurt anybody. It’s a cliché with which occupational health folks and thousands of injured workers would undoubtedly disagree. And while tragic and often preventable physical injuries may be the easiest to see and document, other work-related health risks are much harder to pick up on. One such risk is depression.

Exploring reliable links between work and depression, which is a significant health and economic burden for individuals as well as society, is somewhat murky, as such research is often based on self-reporting methods that can leave wide openings for subjective interpretation. But a new study published in the December 2012 issue of the American Journal of Public Health (AJPH) used two analytic strategies to address such criticism. First, researchers looked for evidence of a dose-response relationship between the number of exposures to adverse work events and the increased risk of depression. Second, they explored whether negative changes in the work environment were tied to the risk of major depressive disorder over the long term.

To put the issue in better context, the Centers for Disease Control and Prevention found that an estimated one in 10 U.S. adults suffers from depression, including more than 4 percent who meet the criteria for major depression. The National Institute of Mental Health reports that major depressive disorder is one of the most common mental illnesses in the nation, and only about half of those with depression receive some form of treatment. Some research has even found that lifetime exposure to major depressive disorder affects people at a cellular level, making them more susceptible to serious and chronic physical illness.

The AJPH study on job strain and depression gleaned its data from the famous Whitehall II study, which followed more than 10,000 British civil servants to examine the social differences in health and disease over a decade. Measuring work characteristics such as decision-making authority, work demands and social support, study authors Stephen Stansfeld, Martin Shipley, Jenny Head and Rebecca Fuhrer found that prevalence rates of major depressive disorder were highest for those who experienced repeated job strain. In fact, exposure to job strain (which was calculated using an equation that considers decision-making ability and work demand) on two or three occasions was linked to a twofold risk of major depressive disorder — a statistic that stood its ground even after researchers adjusted for other social characteristics and behaviors. The authors wrote:

“These findings fit with an exposure time effect model where the longer the exposure to job strain, the higher the incidence of depression. Underlying this hypothesis is the assumption that accumulation of job strain in terms of both time exposed and intensity of job strain increases the risk of depression.”

The study also found that a negative change in job strain was tied to increased prevalence and higher risk of major depressive disorder, and that the “risk (of depression) associated with job strain does not decline immediately despite a beneficial change in working conditions.” This last finding, the authors wrote, may suggest that “once a depressive illness has become established, simple removal of the stressor may not reverse this process.” Authors also took care to note that the data they examined was largely limited to white-collar workers.

In their conclusion, study authors said that preventive interventions in the workplace could make a difference, noting that major depressive disorder costs the U.S. an estimated $97.3 billion every year.

“Job strain is made up of two dimensions that could be modified in the workplace: job demands and decision latitude,” they wrote. “Further research should investigate objective measurement of work characteristics and evaluate the health consequences of interventions in the workplace that are designed to decrease job strain.”

For a copy of the study, visit www.ajph.org.

Kim Krisberg is a freelance public health writer living in Austin, Texas, and has been writing about public health for the last decade.