Evidence-based treatments for major depressive disorder are available, yet show
disappointing results in daily practice. To improve depression outcomes, a primary
care treatment model, collaborative care, has been developed in the USA. Key
elements of collaborative care are: continuous monitoring of symptoms,
collaboration between healthcare professionals and access to a consultant
psychiatrist. Moreover, the role of a care manager is introduced, who coordinates
care, assists in the management of major depressive disorder and monitors
treatment progress. Currently, extensive evidence supports the effectiveness of
collaborative care, and new research projects are studying the effectiveness of
collaborative care in other countries, populations and healthcare settings.
In this study, collaborative care was evaluated in a Dutch occupational
healthcare setting (trial registration: ISRCTN78462860).
Major depressive disorder is a prevalent condition in Dutch occupational
healthcare settings. Dutch workers with major depressive disorder are absent eight
to nine times more often than their colleagues without major depressive disorder.
In The Netherlands, occupational physicians play a central role in the
guidance of workers on sick leave. However, because treatment and sickness
certification are separated in the Dutch legislation, there is a lack of
communication and collaboration between occupational physicians and the curative sector.
Furthermore, access to treatment in specialised mental healthcare is often
hampered by waiting lists. Therefore, occupational physicians aim to play a more
prominent role themselves in the care of workers on sick leave with major
In the present study, the effectiveness of collaborative care, applied by
occupational physician–care managers, is examined for workers with depression on
In this randomised controlled trial (RCT), the effectiveness of a collaborative
care treatment for major depressive disorder was compared with usual care.
Computer-generated randomisation took place at participant level. In both
groups, participants received sickness guidance as usual by their company’s
occupational physician, however, only participants allocated to the
intervention group also received collaborative care from an occupational
physician–care manager. The study protocol, including a power calculation and
the method of masking, is described in greater detail elsewhere.
Workers on the sick list for between 4 and 12 weeks were screened with the
depression subscale of the Patient Health Questionnaire (PHQ-9).
Workers who reached the cut-off score of 10 were contacted for the
administration of a diagnostic interview. Those who met the DSM-IV
criteria for major depressive disorder and gave informed consent were
included. Exclusion criteria are described elsewhere.
The collaborative care intervention consisted of the following elements: 6–12
sessions of problem-solving treatment, manual-guided self-help, a workplace
intervention and anti-depressant medication. The treatment was closely
monitored using the PHQ-9. A web-based tracking system supported the
occupational physician–care manager in monitoring and in adhering to the
protocol. A psychiatrist was available for consultation.
Data were collected at 3 months after baseline by self-report questionnaire.
The primary outcome measure was response, as measured with the PHQ-9 and
defined as a reduction of at least 50% in depressive symptoms.
The PHQ-9 as a continuous measure is also reported.
Data were analysed with logistic and linear multilevel analyses, using MLwiN
software, version 2.15 for Windows XP. Multilevel analyses makes it possible to
take into account the hierarchy of the data, with locations of occupational
physician–care managers constituting the upper level and participants the level
below. Depressive symptom severity at screening was included as a baseline
correction. Post hoc, the intervention effect was explored in
participants with a baseline PHQ-9 score ≥15, by including an interaction term
of that covariate with the intervention variable.
Of 14 595 workers approached, 2955 (20.2%) filled in the screening
questionnaire, of whom 52.5% (n = 1551) screened positive for
depression (online Fig. DS1). Subsequently, 1425 workers were excluded and 126
participants were included and randomised in the usual care group
(n = 61) or collaborative care group (n =
65). Three months after baseline, 98 participants filled in the questionnaire.
Almost two-thirds (62%) of the collaborative care group visited the
occupational physician–care manager and started collaborative care treatment.
Baseline characterisitcs of participants are shown in online Table DS1.
A significant difference was found between collaborative care and usual care in
achieving a response: with 50% response in the collaborative care group and 28%
response in the usual care group, more individuals in the collaborative care
group had at least a 50% reduction in symptoms. The odds ratio was 2.514 (95%
CI 1.035–6.110, P = 0.04). The corresponding number needed to
treat (NNT) is 4.5.
For usual care and collaborative care, the mean baseline PHQ-9 scores were 16.0
and 15.9 respectively (online Table DS2). Three months later, the mean scores
were 9.9 and 8.9. Both groups did not differ significantly from each other
(P = 0.460). In post hoc analyses, a
significant difference in favour of collaborative care was found for
participants with moderately severe symptoms at baseline (P =
0.022, online Table DS3). In that subgroup, participants in the collaborative
care group had a mean improvement from 19.2 to 8.9 (compared with a decrease
from 19.4 to 12.1 in the usual care group). Healthcare utilisation by the
participants is shown in online Table DS4.
The present study showed that collaborative care, applied in the occupational
healthcare setting, was more effective than usual care in terms of response to
treatment among individuals on sick leave with major depressive disorder.
However, for depressive symptoms as a continuous outcome measure, no effect for
collaborative care could be found. In post hoc analyses,
collaborative care was found to be more effective than usual care among those
with moderately severe depression. However, these latter results are secondary
and need to be interpreted carefully and confirmed in future research.
Interestingly, a significant effect was found for the dichotomous outcome
measure, whereas this was not the case for the continuous one. As previously
described by Poirier et al, this discrepancy can be explained
by the variation in the PHQ-9 scores: collaborative care participants were
overrepresented in the groups with a large decrease in symptoms and with no
improvement or a slight increase in symptoms, whereas usual care participants
were in the majority in the group with a moderate decrease of symptoms.
Although response is an internationally recognised outcome measure,
these results can be interpreted as modest since an effect on the continuous
outcome measure is lacking.
The innovation in this study is the new role of the occupational physician as
care manager in the treatment of major depressive disorder. Training and close
supervision were given to them, which, together with the web-based tracking
system, made it easier for them to adopt their new role. However, a substantial
number of the participants did not visit the occupational physician–care
manager. Waiting lists, that had to be operated for collaborative care when the
inclusion of participants increased quickly, may have contributed to this.
Another limitation of this study is the low response rate to the screening
procedure, limiting the generalisability of our findings. This may reflect that
workers on sick leave did not feel the need for a treatment for major
depressive disorder within the occupational healthcare setting. Because of the
separation of treatment and sickness certification in Dutch legislation,
workers were probably not used to the treatment role of the occupational
physician–care manager and a lack of confidence in the occupational physician
may have inhibited them from responding.
This was the first study examining collaborative care provided by occupational
physician–care managers. Given the modest effect of collaborative care on
reducing depressive symptoms and the suboptimal implementation of collaborative
care during the study, further implementation of collaborative care is not yet
justified. Future research needs to confirm whether collaborative care has
added value for individuals with at least moderately severe depression (PHQ-9
This study was funded by the Foundation for Innovation of
Health Insurers (’Innovatiefonds Zorgverzekeraars’) in The
This study was part of the Depression Initiative, a national programme aimed at
supporting depression care in The Netherlands.
Gilbody, S, Bower, P, Fletcher, J, Richards, D, Sutton, AJ.
Collaborative care for depression: a cumulative meta-analysis
and review of longer-term outcomes. Arch Intern
2006; 166: 2314–21.
Katon, W, Unutzer, J, Wells, K, Jones, L.
Collaborative depression care: history, evolution and ways to
enhance dissemination and sustainability. Gen
2010; 32: 456–64.
Vlasveld, MC, Anema, JR, Beekman, AT, van Mechelen, W, Hoedeman, R, Van Marwijk, HW, et al.
Multidisciplinary collaborative care for depressive disorder
in the occupational health setting: design of a randomised controlled
trial and cost-effectiveness study. BMC Health
2008; 8: 99.
Plaisier, I, Beekman, AT, De Graaf, R, Smit, JH, Van Dyck, R, Penninx, BW.
Work functioning in persons with depressive and anxiety
disorders: the role of specific psychopathological
characteristics. J Affect Disord
Anema, JR, Jettinghoff, K, Houtman, I, Schoemaker, CG, Buijs, PC, van den Berg, R.
Medical care of employees long-term sick listed due to mental
health problems: a cohort study to describe and compare the care of the
occupational physician and the general practitioner.
J Occup Rehabil
van der Feltz-Cornelis, CM, Ader, HJ.
Randomization in psychiatric intervention research in the
general practice setting. Int J Methods Psychiatr
2006; 9: 134–42.
Kroenke, K, Spitzer, RL, Williams, JB.
The PHQ-9: validity of a brief depression severity
measure. J Gen Intern Med
2001; 16: 606–13.
American Psychiatric Association. Diagnostic and
Statistical Manual of Mental Disorder (4th
edn) (DSM-IV). APA,
Poirier, MF, Boyer, P.
Venlafaxine and paroxetine in treatment-resistant depression.
Double-blind, randomised comparison. Br J
1999; 175: 12–6.