Working Long Hours May Double Depression Risk

January 30, 2012 — Working overtime appears to be a risk factor for depression, new research shows.

In a prospective cohort study led by Marianna Virtanen, PhD, from the Finnish Institute of Occupational Health, Helsinki, Finland, British civil servants who worked 11 or more hours a day had an almost 2.5-fold greater risk of having a major depressive episode than their counterparts who worked 7 to 8 hours a day.

The study is published online January 25 in PLoS ONE.

The cohort consisted of 1626 men and 497 women who were participants of the Whitehall II study, which aimed to assess the health of London-based civil servants aged 35 to 55 years.

The mean age of the cohort was 47 years at study entry. All the participants were healthy, reporting no symptoms of depression when initially surveyed.

Participants were asked about their work hours. They were followed for a mean of 5.8 years (range, 3.8 - 7.2 years).

At the end of the follow-up period, the workers were screened again. The presence of a major depressive episode during the previous 12 months was assessed using the University of Michigan version of the Composite International Diagnostic Interview (UM-CIDI), which was adapted for a self-administered computerized interview.

"We defined a major depressive episode as a medical diagnosis with 3 core symptoms — depressed mood, anhedonia, reduced energy — and 7 additional symptoms — loss of self-confidence, unnecessary feelings of guilt, changes in appetite or weight, sleep disturbances, difficulties in concentration or indecisiveness, suicidal thoughts or thinking of death, and slowing or agitation of movement," Dr. Virtanen told Medscape Medical News.

Mechanism Unclear

At least 2 core symptoms and at least 4 additional symptoms lasting at least 2 weeks were required for a major depressive episode.

The researchers found that "healthy" employees who worked 11 hours or longer per day at the beginning of the study were 2.43 times more likely to have a diagnosis of clinical depression 4 to 5 years later (95% confidence interval [CI], 1.11 - 5.30), after adjusting for sociodemographic factors at baseline.

After adjusting further for chronic physical disease, smoking, alcohol use, job strain, and work-related social support, the odds ratio was 2.52 (95% CI, 1.12 - 5.65), Dr. Virtanen reported.

The study also showed that a high socioecomic status, which came with an increased likelihood of working long hours, seemed to protect against depression.

"Our findings are in accordance with observations from other studies that showed a positive association between long working hours and depression," Dr. Virtanen said. "But we cannot draw conclusions as to why long working hours are associated with depression from our study."

People should be aware, however, that among many other contributing factors, excessive working hours may predispose to depression, Dr. Virtanen said.

It might also be a good idea for doctors to ask their patients whether they work long hours, and if the answer is yes, to ask whether this is a habit that has lasted a long time, she suggested.

"We do not know whether short periods of long hours at work are harmful. It is also known that many stress factors, when present together, increase the risk of depression. Thus, reducing those factors could be beneficial. At any rate, if people are able to make some changes to the hours they work, it is likely to be better than no change," Dr. Virtanen said.

Downtime Important

Commenting on the study for Medscape Medical News, Dr. Alan J. Gelenberg, MD, Shively/Tan professor and chair of psychiatry at Penn State University, Hershey, Pennsylvania, said that the study marks another step toward increasing understanding of the factors that contribute to depression.

"One of the more interesting aspects is that in this group, which was biased towards British males in white collar jobs, the upper echelon of high-level civil servants seemed immune from this effect, even though they worked long hours," Dr. Gelenberg said.

Stressing that he was speculating, Dr Gelenberg said: "One reasonable possibility is that additional work coupled with the fact that you may not have any control over it could predispose you to depression. That’s why the upper echelons may have been immune; they probably had more control over their work projects."

Dr. Gelenberg added that people who have less control but who are given extra work have additional stress and perhaps less time for the "de-stressing, fun, relaxing things that are part of a healthy lifestyle."

Dr. Gelenberg said that people need time to exercise, to kick back, and to restore their batteries. In addition, he said people need time with their family and that they should get enough sleep. "All of these things contribute to their overall sense of well-being and functioning," he said.

Dr. Virtanen and Dr. Gelenberg have disclosed no relevant financial relationships.

PLoS One. January 25, 2011. Full article

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