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Worldwide, depression is the leading cause of years lived with disability.1 It can affect many aspects of life, including work. In fact, the impact of depression on job performance has been estimated to be greater than that of chronic conditions such as arthritis, hypertension, back problems and diabetes.2,3
Although the disability associated with depression may make it difficult to find and keep a job,4-6 many people who have had a recent depressive episode are in the workforce. In 2002, the majority (71%) of 25- to 64-year-olds who had had a major depressive episode in the previous 12 months were employed and thus potentially dealing with the interference of depressive symptoms on their ability to do their jobs.
Depression has been associated with both absenteeism and decreased productivity (presenteeism). Estimates for the United States have placed the cost of depression at $83.1 billion a year (2000 prices);7 absenteeism and impaired work performance accounted for most of these costs (62% or $US 51.5 billion). In Canada, productivity losses in the form of short-term disability days due to depression, or to depression and distress combined, were estimated at $2.6 billion in 1998.8
This article is based on results from the 2002 Canadian Community Health Survey (CCHS), cycle 1.2: Mental Health and Well-being and the 1994/1995 to 2002/2003 National Population Health Survey (NPHS) (see Methods and Limitations). The prevalence of depression among employed Canadians aged 25 to 64 is estimated by selected characteristics (see Definitions). To assess the impact of depression in the workplace, associations with reduced work activities, disability days, and work absences are examined in multivariate models that control for sociodemographic factors, job characteristics, and physical and mental health.
In this analysis, work impairment covers both “absenteeism” and “presenteeism.” Absence from work in the past week is used as a measure of absenteeism, and reducing work activities is a measure of presenteeism. A third variable — at least one disability day in the past two weeks — combines elements of both, in that it measures days spent entirely in bed (absenteeism) and days when respondents had to cut down on activities or expend extra effort to perform them (presenteeism).
According to the 2002 CCHS, 3.7% of people aged 25 to 64 who were employed at the time of their interview (an estimated 489,000) had experienced an episode of depression in the previous year (Table 1). An additional 8% of employed people (1.05 million) had had a depressive episode sometime in their lives, but not in the previous year (data not shown).
As in the general population,17-25 depression among workers was approximately twice as prevalent among women as men (Table 1); less prevalent among those who were married or in a common-law relationship (Table 1); and more prevalent among those who lived in lower-income households (Table 1). Differences by age and education were not significant.
Earlier studies have reported that depression is associated with both physical and mental comorbidity.21,25,26 Results from the 2002 CCHS were similar. Workers with chronic conditions or alcohol or drug dependence (past 12 months) or anxiety disorders (past 12 months and lifetime) were more likely than those who did not have these problems to report that they had had a depressive episode in the previous year. Excess weight, however, was not associated with depression among workers.
A number of job-related factors — occupation, hours of work, shift work and work stress — were associated with depression.
White-collar workers and those in sales/service were more likely than blue-collar workers to have suffered from depression (Table 1). This is in line with other studies that found differences in the prevalence of depression by occupation.19,27-31
The prevalence of depression was relatively low among workers who spent more than 40 hours a week on the job, but relatively high among those who worked less than 30 hours, a discrepancy that may reflect the impact of mental health on hours worked. Individuals who had had a depressive episode in the previous year may not have been able to work a full week, while those who did not have such an episode may have been able to work longer hours.
Consistent with earlier research that found a link between mental health and shift work,32 the prevalence of depression was higher among evening and night workers than among those with a regular day schedule.
And, according to the CCHS, employed people who characterized most days at work as stressful were more likely than those in less stressful work situations to have had a depressive episode in the previous year (see Stress, coping and support). Other research, too, has shown work stress to be related to depression and other psychological disorders.33‑35
CCHS respondents who had had a depressive episode in the previous year were asked how much, on a scale of 1 to 10, it had interfered with several aspects of their lives during the period when the symptoms had been most severe. They were also asked how many days depressive symptoms had rendered them totally unable to work or carry out normal activities.
Most workers who had experienced depression in the year before they were interviewed (79%) reported that the symptoms had interfered with their ability to work to at least some degree. Almost one in five (19%) had experienced very severe interference (score of 10) (Table 2). On average, depressed workers reported 32 days in the past year during which the symptoms had resulted in their being totally unable to work or carry out normal activities.
The marked degree to which depression interfered with functioning at work is not surprising. The symptoms of depression can include fatigue or lack of energy, loss of interest, diminished ability to think or concentrate, and feeling sad, discouraged or hopeless. A number of crucial elements of job performance are particularly vulnerable to such symptoms, for instance, time management, concentration, teamwork, and overall output.36
Nonetheless, one in five (21%) workers who had experienced depression in the previous year said it had had no effect on their ability to work (Table 2). Even more (40%) reported never having had a day during which they had been totally unable to work or carry out normal activities. It may be that, for these workers, symptoms had not been severe enough to interfere with their duties, or that the impact had been greater on other aspects of their lives. In fact, consistent with earlier research,25 the mean interference score of depressive symptoms was higher for social life and home responsibilities than for the ability to work (Table 3).
Days totally unable to work, however, likely underestimates the impact of depression on job performance. This measure does not capture days when respondents came to work but could not fully carry out their assignments. In other studies, mental disorders were found to be more strongly related to days during which workers had to expend extra effort or cut back on work activities rather than to days of complete work loss.29,30,37,38 As well, the former account for a greater proportion of the total economic costs of mental disorders to employers.38
Workers who had experienced depression were more likely than those who had no history of depression to report several specific forms of work impairment: reduced activities due to a long-term health condition, at least one mental health disability day in the past two weeks, and absence from work in the past week (Chart 1) (see Work impairment).
Compared with workers with no history of depression, those who had had an episode in the previous year were almost three times as likely to report reduced work activities because of a long-term health condition (29% versus 10%). Even workers who had not experienced depression in the previous year but who had a lifetime history of depression were at increased risk of reducing their work activities (16%). However, workers with a history of depression may have intentionally cut back their activities, perhaps to reduce work stress and to minimize the risk of another episode. They could also have been experiencing sub-clinical depression, which has been linked to functional impairment.2,39
Depression was also strongly related to mental health disability days: 13% of workers who had experienced depression in the previous year reported at least one day in the past two weeks when, because of emotional or mental health or the use of alcohol or drugs, they had had to stay in bed, cut down on normal activities, or their daily activities took extra effort. By contrast, only 1% of workers with no history of depression reported a mental health disability day.
Work absences were far more common among people who had experienced depression in the previous year than among those with no history of depression. While 16% of workers reporting a recent episode had been absent the past week, the figure was 7% for those who had never had a depressive episode.
Depression is often accompanied by other psychiatric illnesses, substance abuse or physical conditions that can impede an individual’s ability to work. To determine if the associations between depression and work impairment were statistically significant, multivariate models that controlled for these factors and other possible confounders such as socio-demographic and job characteristics were used. Even when the effects of all these factors were taken into account, the associations between depression and work impairment persisted: workers who had had a depressive episode in the previous year had more than twice the odds of reduced work activity and work absence, and six times the odds of reporting a mental health disability day, compared with those who had no history of depression (Table 4).
The association between depression and work impairment may be particularly strong for people in specific employment situations. Consequently, the models for work impairment were rerun with interaction terms between depression and occupation, working hours and work schedule.
The interaction between depression and white-collar occupations was positive for reduced work activities (odds ratio 2.88; 95% confidence interval 1.36 to 6.12). That is, although white-collar workers were generally less likely than blue-collar workers to reduce their work activities (Table 4), white-collar workers who had had an recent episode of depression were actually more likely to do so (data not shown). This difference may reflect a greater impact of depressive symptoms on activities that are more common in white-collar jobs, compared with other occupations.
An association between depression and reduced work activities also emerged for people who regularly worked evenings or nights rather than days (odds ratio 2.88; 95% confidence interval 1.04 to 7.95). A previous study showed relationships between working an evening shift and psycho-social problems, chronic conditions, sleep problems, and distress.32 Thus, it may be that depressive symptoms compound the impact of other health problems that are associated with shift work, thereby resulting in greater work impairment.
In numerous studies, coping strategies and levels of support have been associated with the risk of depression and other mental illnesses.41-47 Few studies have examined whether these factors are related to the job performance of workers with mental disorders.
CCHS results show that workers who had had a recent depressive episode often used different coping mechanisms than did other workers (see Stress, coping and support). Workers who had had a depressive episode were more likely to report that they cope with stress by avoiding people, using negative means of tension reduction (such as smoking or drinking more than usual), blaming themselves or wishing it would go away; they were less likely to talk to others or “look on the bright side” (Table 5). As well, workers who had experienced depression in the previous year were more likely than those who had not to report that they had low levels of co-worker support, supervisor support and emotional social support.
In multivariate analysis, most of these coping behaviour and support variables were associated with work impairment among employed people overall (Table 6). But when only workers who had had a depressive episode in the previous year were considered, just two variables were significant: looking on the bright side and low co-worker support.
Looking on the bright side reduced the odds that workers with depression would have had at least one mental health disability day in the past two weeks. However, it is possible that the coping strategies included in the CCHS are influenced by depressive symptoms. Because depressed people often have a negative perspective, the association with looking on the bright side may reflect workers with mild, rather than severe, depression.
Low co-worker support increased the odds that depressed workers would have been absent from work in the previous week. But because this analysis is cross-sectional, the direction of the association cannot be determined: it is not clear whether low co-worker support influenced work absence or vice versa.
With cross-sectional data, it is not possible to say if depression leads to work impairment, or if workers who are limited in what they can do on the job are more likely to experience depression. Longitudinal data from the National Population Health Survey (NPHS) can shed some light on the temporal sequence of these events.
Compared with workers who had not had a recent depressive episode, the odds were high that those who had experienced depression in the 12 months before their NPHS interview would report reducing work activities or taking disability days at follow-up two years later (Table 7). This association suggests that the effects of depression on job performance can be long-lasting.
A 2005 study also found that many people in remission from a depressive episode still experience symptoms that affect social functioning.53 But according to another study, the impact of residual symptoms on work resolved in 6 to 12 months.54 In the NPHS longitudinal model, it was not possible to control for psychiatric comorbidity, which may have played a role in the development of a new case of work impairment.
Based on data from the 2002 Canadian Community Health Survey, nearly half a million workers aged 25 to 64 (close to 4%) had had an episode of depression in the previous year, and an additional million had experienced depression at some point in their lives.
Consistent with other research,4,19,37,38,55-57 data from the Canadian Community Health Survey and the National Population Health Survey suggest that depression is associated with work absences and with lost productivity in the form of reduced activity. The cross-sectional and longitudinal analyses both show that depression has associations with work impairment that persist even when the effects of sociodemographic, job and health characteristics are taken into account.
The findings in this article highlight the importance of white-collar occupations and night/evening work schedules in the link between depression and work impairment. As well, coping by “looking on the bright side” and co-worker support may buffer the impact of depression on job performance.