Two potential limitations of this study are the possible existence of inaccuracy in the key measures and the possible existence of unmeasured common causes of the disorders and outcomes. With regard to the first of these two, accuracy of diagnostic assessment was documented in the SCID reappraisal interviews mentioned in the section on measures. However, fully structured instruments like the CIDI are less able to distinguish mixed episodes than are semi-structured clinical interviews, leading to the imposition of a more rigid distinction between MDE and manic-hypomanic episodes in BPD than would have been ideal (30
). Accuracy of the HPQ work performance assessment was evaluated in a series of workplace validity studies (25
) that documented strong relationships of HPQ measures with independent payroll records and supervisor evaluations of job performance.
The possibility of unmeasured common causes is much more difficult to evaluate. To the extent that common causes exist, the estimated effects of BPD and MDD on lost work performance will be biased. No definitive way exists to evaluate this possibility other than by experimentally changing the prevalence of these disorders, presumably in a treatment effectiveness trial, and evaluating effects on work performance. Results of such experiments in representative workplace samples have not been reported either for BPD or MDD, although such an experiment is currently underway to evaluate the workplace effects of treating MDD (31
). Despite the absence of experimental evidence, simulations of likely effects have been carried out using parameter estimates gleaned from clinical trials (32
). The estimated decrements in work performance associated with MDD in these simulations are broadly consistent with the NCS-R estimates. In addition, the results of a recently reported experimental effectiveness trial aimed at increasing work performance by improving quality of MDD treatment yielded estimates of effects on work performance broadly consistent with the NCS-R estimates (34
Within the context of the above limitations, the results reported here show that BPD and MDD are both common disorders in the US civilian labor force associated with substantial lost work performance. Our prevalence estimates of BPD and MDD are consistent with those in other recent national surveys (35
). As noted in the introduction, though, bipolar spectrum disorders could be defined more broadly than in the current report (3
). The same is true for sub-threshold depression, (37
). Future research should investigate the effects of these sub-threshold disorders on work performance (5
Our finding that both BPD and MDD are associated with substantial losses in work performance is broadly consistent with other surveys of workplace costs (12
). The estimated annual population-level workplace cost of MDD, $36.6 billion, is in the range of the two other recent studies that estimated the workplace costs of MDE -- $31.0 billion (31
) and $51.5 billion (12
). The larger of these two is probably upwardly biased because it is based on an analysis of days out of role (i.e., including weekends) rather than days out of work. No previous estimates of the population-level workplace cost of BPD are available to compare to our $14.1 billion estimate.
By considering BPD and MDD simultaneously, we documented that BPD is associated with substantially more lost work performance than MDD at the individual level, although aggregate impairment is greater for MDD than BPD because of the higher prevalence of the former than latter disorder. Decomposition showed that the higher individual-level impairment of BPD than MDD was due largely to MDE being more impairing in the context of BPD than MDD rather than to mania-hypomania being more impairing than MDE. The finding that mania-hypomania in the absence of MDE is associated with significantly less work impairment than BPD with MDE is consistent with the observation in a prospective patient study that functional impairment was associated with variation in depressive symptoms but not manic symptoms (42
). More detailed analysis of the NCS-R data shows that the higher individual-level work impairment of MDE in BPD than MDD is due partly to the greater persistence and severity of MDE in BPD than in MDD. However, persistence-severity of MDE explained only part of the association between BPD and work impairment. The remaining part of this association could be due either to imprecision in our measures or effects of unmeasured correlates of BPD and work impairment.
An important practical problem related to the finding that most workers with BPD had MDE is that MDE due to BPD is sometimes incorrectly treated as if it was due to MDD (43
). This problem is exacerbated by people with BPD reporting more distress due to their depressive than their manic symptoms (40
). As antidepressant medications can trigger the onset of mania, it is important to screen for history of BPD at the initiation of depression treatment. A short and valid screen for manic-hypomanic symptoms has recently been developed that could be used for this purpose (45
). It is important for the same reason to include a screen for BPD in workplace depression screening programs. The prevalence and impairments of sub-threshold cases should also be examined. Effectiveness trials are needed to calculate the return on investment from the employer perspective of coordinated workplace BPD-MDD screening and treatment effectiveness trials (34