Introduction
Depression is a widespread, disabling psychiatric illness with far-reaching personal and economic consequences [
1,
2]. By the year 2020, depression will be the second largest burdensome illness in developed economies [
3]. In addition to its adverse individual effects, the associated workplace effects of depression are extensive. Employees with depression report significantly more health-related lost productive time than those without depression [
4‐
6], higher rates of absenteeism and short-term disability spells [
7], and higher rates of job turnover [
8]. Economic analyses have consistently demonstrated that the costs of lost productivity associated with depression far exceed the costs of resources utilised to treat and manage the disorder [
9]. Furthermore, depression has been shown to be one of the most costly of common health conditions that affect the ability to work and work (or job) performance [
5,
10‐
13].
Not surprisingly, many employers offer Employee Assistance Programs, health promotion or wellness programs, yet employer-sponsored programs that specifically target depression in the workplace remain uncommon [
14]. There are information gaps that may prevent employers from making further investments to reduce the impact of depression in the workplace. The most significant gap may be the paucity of readily accessible information on targeted interventions that improve work-related outcomes, such as reducing absenteeism and productivity loss at work [
13]. Consequently, we undertook a systematic review to identify evidence-based programs, or intervention approaches that could be implemented or facilitated by employers to manage workers’ depression and reduce associated productivity losses.
Methods
The systematic review methods were adapted from a process developed by the Cochrane Collaboration [
15]. The review team included 11 researchers from Canada, United States, and Europe from various disciplines. The research question addressed was: “Which intervention approaches to manage depression in the workplace have been successful and yielded value for employers in developed economies?”
Stakeholder Engagement
Two meetings with stakeholders (representing the Ontario Ministry of Health and Long-Term Care, the Ontario Ministry of Government Services, insurance providers, disability management service providers, mental health organisations, mental health disorder survivors, organised labour, and employers) were conducted to solicit input related to the research question, literature search terms, presentation of the findings, messages, and appropriate communication channels.
Criteria for Inclusion of Studies
The review team considered published or in-press peer-reviewed scientific articles. There were no language restrictions. Book chapters, dissertations, and conference proceedings were excluded.
Search Methods for Identification of Studies
Key terms were identified and combined to search the following databases from their inception dates: MEDLINE, EMBASE, CINAHL, Central, PsycINFO and Business Source Premier up to June 2010. Both database-specific controlled vocabulary terms and keywords were included. The complete list of terms used and the detailed search strategy are presented in Appendix 1—Electronic supplementary material. The reference lists in review articles and articles included were also checked.
Selection of Studies, Risk of Bias Assessment, and Data Extraction
Study selection, risk of bias assessment, and data extraction were conducted independently by two members of the review team in rotating pairs that were randomly selected from the pool of 11 authors. All authors participated in all tasks. Titles, abstracts, and full articles were evaluated to exclude articles that did not meet the inclusion criteria (Appendix 2—Electronic supplementary material). Reviewers entered responses for all levels of review on commercial review software, DistillerSR [
16], allowing centralised article tracking and access.
Risk of bias was conducted using a protocol adapted from the Cochrane Collaboration. Responses from 18 quality criteria questions (Appendix 3—Electronic supplementary material) were grouped to form a set of criteria used to judge risk of five biases: (1) selection bias; (2) attrition bias; (3) performance bias; (4) measurement bias; and (5) reporting bias [
15]. For each type of bias, the risk was determined to be low, moderate, or high. An article was considered to be overall at high risk for bias if the risk of any one bias type was rated high.
Data were extracted using a standardised data extraction form based on existing forms and data extraction procedures [
17,
18]. A classification framework was established to categorise the work-related outcomes reported in the studies of this review into one of four categories, as suggested by stakeholders (see Table
1). Quantitative pooling of results was not possible due to outcome measure heterogeneity, study methods, and lack of data necessary to calculate effect sizes.
Table 1
Framework of work-related outcomes relevant to review stakeholders
Relevant study population | Depressed workers, currently working and not on work disability leave/sickness absence | Depressed workers currently on work disability leave/sickness absence due to their depression | Depressed workers, currently working and not on work disability leave/sickness absence | Depressed workers who are currently working, but have had a prior episode of work disability/sickness absence due to their depression |
Among this study population, is there an effective intervention to: | Promote stay at work, promote job retention, or prevent or reduce the number of casual sick leave days taken due to depression (e.g., use of vacation days or unpaid sick days) or paid sickness absence days? | Promote a return to work, hasten a return to work, prevent the transition from short-term work disability leave to long-term leave, or prevent the transition from sickness absence to work disability? | Maintain or improve a worker’s functioning both in terms of productivity and performance? | Prevent or reduce recurrences of work disability leave/sickness absence due to depression? |
Outcome measures | Number of causal sick leave days or vacation days Number of paid sickness absence or sick leave days Hours worked Job retention Transition to work disability leave | Return to work Duration on work disability leave/sickness absence Transition from short-term disability to long-term disability Transition from sickness absence to work disability | Productivity and performance measures (e.g., Work Ability Index, Health and Work Performance questionnaire) | Recurrence of work disability/sickness absence Number of work disability/sickness absence recurrences Duration of a recurrent work disability leave/sickness absence |
Evidence Synthesis
The quality of evidence and strength of recommendations were adapted from the Grading of Recommendations Assessment, Development and Evaluation Working Group [
19]. (Appendix 4—Electronic supplementary material) The summary of findings and key messages were developed following published guidelines from the Cochrane Collaboration [
15]. For each intervention assessed, the findings corresponding to each work-relevant outcome category were classified as positive, negative, or neutral, depending respectively upon whether the intervention group was statistically significantly better (
P < 0.05), worse (
P < 0.05) or not different (
P ≥ 0.05) from the control group. Key messages for each intervention approach were extracted following the framework shown in Table
2 for those studies employing an inactive control group (e.g., usual care).
Table 2
Translation from summary of findings to key messages
High | Intervention is consistently better* than inactive control | Recommendation to implement the intervention |
| Intervention is consistently inferior to inactive control** | Recommendation against implementation of the intervention |
Moderate or low | Intervention is consistently better than inactive control | Practice consideration or promising practicea
|
| Intervention is consistently inferior to inactive control | No recommendation. Need for more research |
Very low | Intervention is consistently better than or inferior to inactive control | No recommendation. Need for more research |
Any | Findings are mixed*** or contradictory**** | No recommendation. Need for more research |
Discussion
Our systematic review was designed to answer the question: “Which intervention approaches to manage depression in the workplace have been successful and yielded value for employers in developed economies?” We included ten randomised trials and two non-randomised studies from various countries and jurisdictions that evaluated a wide range of intervention practices to manage the impact of mild to moderate depression in the workplace. The evidence derived from all studies and intervention approaches for the primary outcomes of interest was graded as “very low” in all cases. A combination of factors contributed to this grade of evidence: the high risk of bias in all included studies, the paucity of studies for each outcome, which affected the consistency and precision of the evidence, and populations and outcomes that do not directly generalise to the population of interest. In addition, it was challenging to integrate data across diverse disability insurance and health care systems.
Consequently, there is no one intervention that we have found that can be recommended as effective for the four main outcomes suggested by the stakeholders (prevention and management of work disability/sickness absence, work functioning and recurrences of work disability/sickness absence).
The results from our review are consistent with those of one recently published Cochrane review that evaluated the effects of interventions aimed at reducing sickness absence/work disability in depressed workers [
35]. They concluded that there was no evidence of an effect of medication alone, enhanced primary care, psychological interventions or combinations on sickness absence of depressed workers. Other recently published systematic reviews were not focused on depression [
36,
37], or did not focus on working populations [
38,
39]. Others focused on clinical (e.g., improvement in depression) or process of care outcomes (e.g., medication adherence), rather than work-related outcomes of more direct relevance to workplaces [
40,
41]. Examples of such outcomes have been previously described using a classification framework informed by stakeholders of Ontario’s health and safety system (Table
1) and may be informative for future research in this area. There are narrative reviews [
42,
43] concluding that cognitive-behavioural therapy and interpersonal therapy reduce work disability and are cost-effective.
It is interesting to note that the majority of the included studies were not “workplace-based” or “work-directed” in terms of the setting or approach. Most studies concerned clinical interventions focused on the individual worker, often within the (collaborative or enhanced) health care setting. These clinical interventions might be implemented or facilitated by the employer to manage depression in the workplace—depending on the health care and jurisdictional context. However, along with the worker-focused intervention approaches which might be feasible and need further evaluation, particular challenges and barriers in the implementation of interventions to manage depression in the workplace have to be addressed. For example, in their recent report on best practices for return-to-work/stay-at-work interventions for workers with mental health conditions, Pomaki et al. [
36] conclude among others that more research is needed to better understand stigma and discrimination, to increase supervisor and co-worker awareness and support, and to focus on work and the workplace. Future studies might consider to combine organizational-level interventions with work(er-)-focused interventions.
It is not yet known the optimal timing of the intervention in the course of a depressive episode, and the duration of the intervention’s effect. It is unknown whether the positive results reported in some studies generalise to different compensation and health care systems. The review clearly showed the challenges in the definition and interpretation of work-related outcomes (such as sickness absence or work disability) across studies from different jurisdictions. Interventions and programs aiming at these work-related outcomes are shaped by the health care and jurisdictional context, and may not be directly relevant to other jurisdictions.
Strengths and Limitations of the Review
Our review was conducted by an international and multidisciplinary team, who received input and feedback from a Canadian stakeholder group. Stakeholder involvement was essential in shaping the research question, suggesting terms for the literature search, prioritising outcome measures, and interpreting the key findings.
Even though we used a comprehensive search with broad inclusion criteria, it is possible some relevant studies were still missed. We used a validated method to judge the risk of bias of the included studies, but the judgments are in most cases subjective. Our choice to do a qualitative synthesis instead of a meta-analysis pooling was directed by the type of data, but it could have been argued that our choice was not the most appropriate.
Given the prevalence of depression in the workplace and the costs associated with work disability and productivity loss at work, even a small effect size with economic benefits may be regarded as relevant to employers and employees. Although ten of the 12 included studies used a randomised controlled design, there were many features of study design, study performance or analyses that jeopardised validity. For instance, due to the inherent nature of these interventions, all included studies lacked the ability to appropriately blind intervention providers and participants to the intervention, introducing the risk of performance and measurement biases. Several studies featured inadequate descriptions of participation and adherence to the proposed interventions, potential differences between participants and non-participants, potential differences between remaining participants and those lost to follow-up, or the methods used to randomly allocate individuals. Contamination was also a problem in several studies, while some studies did not account for baseline differences between groups in the analysis.
Implications
Future studies should reduce the risk of bias by focusing on randomised trials, blinding, and to adhere to the CONSORT standards for description and reporting [
44]. Blinding participants to the intervention received is challenging, but cluster randomisation may facilitate this. Future studies should also describe the baseline working status (working or on disability/sick leave) and attempt to report the result for each distinct baseline working status in order to more specifically address whether an intervention is effective to prevent work disability/sickness absence or to manage work disability/sickness absence. There is also a need for valid and reliable outcome measures, and a consensus on what should be measured when approaching productivity or loss of productivity at work.
The problem of depression in the workplace is complex, with consequences to the worker and their families, co-workers, supervisors and employers, disability insurers, and government. No single intervention approach was shown to be effective to manage workers with depression, but the current review provides some direction for future research in terms of types of feasible interventions, study design, and framework for outcome measures.
Acknowledgments
Nancy Carnide is supported by a Canadian Institutes of Health Research Vanier Canada Graduate Scholarship. Kimberley Cullen is supported by a National Sciences and Engineering Research Council of Canada Graduate Scholarship. The team is grateful to Quenby Mahood and Joanna Liu for their assistance with literature searches and article retrieval. We would also like to thank all of the stakeholders who participated in our two meetings.