Work-related Factors Affect Risk of Major Depressive Disorder Differently in Men and Women

A study using multiple data models finds several common factors associated with work stress and satisfaction may contribute to depression risk in men and women via different mechanisms.

Several studies have investigated potential links between work-related factors (job-related stress, degree of work autonomy, number of hours worked, etc) and the risk of developing major depressive disorder. However, many of these studies have been poorly controlled, relied on only one model, and/or did not sufficiently account for potential sex differences.

There are three widely used models in general occupational health research:

• The demand-control model, which posits that “negative health outcomes, such as fatigue, depression, and other physical illnesses, result from situations in which one’s control over one’s work is low and the psychological demands imposed by one’s work are high.”
• The effort-reward imbalance (ERI) model, which assumes that “the experience of a lack of reciprocity in terms of high costs and low gains elicits negative emotions in exposed people” (ie, feelings of being unappreciated plus inadequate rewards are often accompanied by “sustained strain reactions in the autonomic nervous system”).
• The work-to-family conflicts model, which posits that “impediments to work- and family-related identity formation and maintenance are likely to be experienced as stressful,” thus making work-to-family conflicts a potentially important risk factor for major depression.

The authors of “A Population-based Longitudinal Study on Work Environmental Factors and the Risk of Major Depressive Disorder,” published in the July 1 issue of the American Journal of Epidemiology (http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3385158/?tool=pubmed), undertook to use these three models to “investigate the relations between work environmental factors and the one-year risk of major depressive disorder (MDD) and to examine whether the work environmental factors associated with the risk of MDD differ by sex.” The study was “the first population-based longitudinal study that incorporated three widely used occupational health models and assessed MDD using a structured diagnostic interview.”

For the study, the researchers recruited adults between the ages of 25 and 65 who resided in Alberta, Canada. Nearly two-thirds of the participants worked in the oil and gas industry, the service industry, or government service. To exclude subjects who already had MDD, participants were screened using the World Health Organization’s Composite International Diagnostic Interview, resulting in a cohort of 2,752 subjects who were free of current and lifetime MDD at baseline.

Participants completed the Job Content Questionnaire (http://www.jcqcenter.org), which assesses level of work stress by asking questions that cover decision latitude, skill discretion, psychological demand, job security, and social support from supervisors and coworkers. Higher scores on the JCQ scales indicate higher levels of job-related stress. The authors also used the JCQ scores in the areas of psychological demand, skill discretion, and decision authority to compute a “job strain ratio (JSR),” in which a higher ratio represents a situation where the psychological demands of a participant’s job exceed his or her perception of autonomy and authority in the job setting.

They also calculated an ERI ratio for participants that measured the imbalance between effort and reward on the job. The researchers also administered scales that measured work-to-family conflict and family-to-work conflict.

The authors estimated the one-year incidence of MDD overall and by sex among participants who had no lifetime or current MDD at baseline, analyzing the data to identify “baseline factors associated with the new onset of MDD.” They reported that the weighted one-year overall incidence of MDD was 3.6% (2.9% in men and 4.5% in women).

In their discussion of their results, the authors wrote that “We found that JSR, ERI, and work-to-family conflicts might affect the risk of MDD through different mechanisms. The relation between JSR and MDD was not linear and varied by sex. Similarly, there was a sex difference in the relation between ERI and the risk of MDD. High JSR, low job security, and family-to-work conflict lead to a higher risk of MDD in men. In women, working 35—40 hours per week and having high levels of ERI, job insecurity, and work-to-family conflict were the risk factors for the onset of MDD.”

They concluded that “JSR and ERI are common in workplaces and can contribute to the risk of MDD. Howe