The results suggest that enhanced depression care of workers has benefits not only on clinical outcomes, but also on workplace outcomes. Although direct comparison to earlier studies is difficult because our trial is the first conducted exclusively among employed people, it is noteworthy that our effect size on clinical improvement (approximately one-third of a SD on the QIDS-SR distribution) is similar to earlier primary care trials using low-to-moderate intensity interventions.35, 39, 40
Our finding of effects among less-severe as more serious cases is consistent with earlier primary care trials41, 70
and suggests the intervention has benefit to a wide spectrum of depressed workers.
The significant 2.6 hour improvement per week in overall work functioning among intervention subjects is due to a combination of increased job retention and increased hours worked among the employed. Earlier analyses of working sub-samples in primary care trials have found generally comparable effects on retention41
Although we did not find significant effects on work performance among the employed by one year, one primary care trial that followed patients for two years did.36
The apparent effects on absenteeism and performance among the employed in our trial may also have been downwardly biased if the intervention led to retention of employees with more absences or worse performances. Unfortunately, direct comparisons with these earlier studies are difficult due to differences in intervention intensity, follow-up, and stratum definitions.
Formal evaluation of our intervention's return-on-investment to employers is not currently possible, as the latter requires information not yet available on duration of improvements, disability payments, overall healthcare expenditures, and hiring and training costs. However, the $1800 annualized value of higher mean hours worked among intervention subjects retaining their jobs (assuming the median annual salary in the U.S. civilian labor force) by itself far exceeds the $100–$400 outreach and care management costs associated with low-to-moderate intensity interventions of the sort we implemented38, 39
; these saving might also exceed or closely approximate the costs of approximately 10 additional mental health specialty visits made by intervention subjects over the course of a year.
These last observations suggests that outreach and enhanced care for depressed workers might be better conceptualized as an opportunity to invest in improving the productive capacity of workforces (referred to by employers as “human capital investments”) than as workplace costs.72, 73
That the intervention also had positive impacts on job retention and the costs of hiring and training new workers are typically high1
reinforce this interpretation.74
However, it is important to recognize that these workplace benefits would not be realized by all employers, as hiring and training costs and extents to which employees are paid piecemeal, hourly, or by salary do vary.
The intervention had modest effects on self-reported use of treatments, consistent with earlier trials of low-intensity interventions.38, 39
However, intervention subjects received twice as many contacts as usual care subjects when care manager contacts were included (12.7 vs. 6.5, t = 5.7, p < .001) and were 70% more likely to receive any mental health specialty treatment. Although it is difficult to identify active components from a trial with a single intervention arm, the finding that intervention subjects received more mental health specialty treatment is noteworthy in light of other data suggesting that mental health specialty care is more likely to meet evidence-based recommendations than treatments in other sectors.25
A recent meta-regression of 28 depression collaborative care trials is also instructive in that it identified three “active ingredients”: systematic screening to identify patients (vs. other means such as clinician referral), use of mental health professionals as care managers, and regularly planned care manager supervision.27
All three elements were included in our intervention. The telephone CBT may also have been beneficial, as an earlier trial found a higher proportion of patients experiencing depression improvement in care management plus telephone CBT than in care management alone.38
Several potential technical limitations are noteworthy. First, the QIDS-SR might have misclassified cases, although clinical reappraisal studies show it has high concordance with blinded clinician assessments.49–51
Second, the HPQ might have been systematically biased,75
although significant associations between HPQ scores and independent administrative/archival records of absenteeism and work performance have been documented across a broad range of occupations.65, 66
Third, workers who participated in our initial screening phase may have had a different prevalence, severity, or impairment associated with their depression than non-participants, While we had no way to evaluate this possibility, a prior study found initial participants in HRA screenings were comparable to initial non-respondents who participated only after more intensive recruitment efforts in terms of depression severity, work impairments, and associations between the two.76
Fourth, the generalizability of our findings is unclear, as trial participants had less severe depressions and a different socio-demographic profile than a nationally representative sample of depressed workers. Although we found no differences in intervention effects across levels of depression severity or method of recruitment, such differences could exist across other subgroups (e.g. white vs. blue collar workers) and have relevance to employers whose workforces vary in these characteristics.
Potential conceptual limitations also need to be considered. Simple human capital metrics such as absenteeism and job performance might overestimate
true costs to employers, as would happen if unperformed work during absences is made up by coworkers or the absent worker upon return.77
However, it is also possible that the burdens of depression to employers are underestimated
here because other costs, such as for hiring temporary workers, paying coworkers overtime, and adverse effects on coworkers' productivity were not considered.78
Likewise, we did not assess intervention effects on outcomes such as suffering, marital stability, caregiver burden, and employee contributions outside the workplace that could have value from a societal perspective and might lead to long-term improvements in productive capacity.79
An exclusive focus on work outcomes might devalue benefits of intervening among groups not in the workforce (e.g., the elderly) or in low-wage occupations, emphasizing that healthcare resource allocation decisions need to consider a societal as well as employer perspective. Within the constraints of these limitations, this study suggests that enhanced depression care for workers can have benefits for employers that go beyond improved health and diminished suffering in their workforces and extend to increased work productivity. Further study is needed to determine if intervention costs are offset by these workplace benefits and the variation in this offset across different employment settings.72, 73
Toward this end, it is noteworthy that increased depression treatment among intervention subjects was largely telephone contacts with care managers and not more expensive in-person visits with traditional providers. We also did not consider if the intervention offsets any greater general medical utilization associated with depression, as has been observed in earlier primary care trials.32, 34, 35, 82
Likewise, availability of web-based, e-mail, and interactive voice-recognition technologies should ensure the costs of screening and recruiting depressed workers into interventions are low.83
These features may be critically important to potential purchasers, who are not just sensitive to interventions' returns-on-investment but also their absolute costs and impacts on per-member per month (PMPM) charges.44
Attention to these issues in future research is needed to ensure that successful programs of outreach and enhanced depression treatment are widely disseminated.45