Better together: how collaborative working can improve outcomes for patients with depression and diabetes

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The link between depression and diabetes mellitus (DM) is well established. Around 20% of patients with DM meet diagnostic criteria for depression. The National Institute for Health and Care Excellence (NICE) issued guidance impressing the importance of diagnosing and treating depression in long-term conditions such as DM (NICE, 2009). However, depression in the presence of physical illness is often missed and under treated.

One way of improving this situation could be through collaborative care (CC). The NICE guidelines CG91 state that CC should form part of a well-developed stepped-care programme for people with moderate to severe depression and a long-term condition. CC requires joint working between the patient and healthcare professional to identify problems and agree goals for interventions.

Around 20% of patients with diabetes meet the diagnostic criteria for depression

Around 20% of patients with diabetes meet the diagnostic criteria for depression

It is recommended that CC models comprise of:

  • Case management (supported by a senior mental health professional),
  • Multi-professional collaboration (between primary and secondary physical health services and specialist mental health),
  • A range of evidence-based interventions,
  • And long term coordination of care and follow-up.

A research group from China, have evaluated CC for depression and diabetes in their recent systematic review and meta-analysis (Huang, 2013).


A literature search of randomised controlled trails (RCTs) was conducted using the appropriate biomedical databases (Medline, Embase, Cochrane and PsychINFO) and references were screened from retrieved articles. Most inclusion criteria were broad (such as age) but participants required a diagnosis of depression (or a history of treatment with an antidepressant) and a diagnosis of DM.

The outcomes of interest evaluated at 6 and 12 months were;

  • depression treatment response (a 50% or more decrease in the Hopkins Symptom Check-List-20 score from baseline);
  • depression remission (a Hopkins Symptom Check-List-20 score of less than 0.5;
  • HbA1c;
  • antidepressant and/or oral DM medication adherence (percentage of prescribed doses taken with a threshold of 80%).

Mean differences (MDs) were calculated for HbA1c values and relative risks (RR) for depression outcomes and medication adherence. Either a random effect or fixed effects model was used to calculate the pooled effects of the RCTs.


Two authors screened the search results. Out of 1462 citations 8 studies were included in the meta-analysis. RCT duration varied between 13-30 months.

Depression outcomes

4 trials reported:

  • A significant increased treatment response in the CC group (RR = 1.96, 95% CI = 1.38 to 2.78)
  • A significant beneficial effect of CC at 6 (RR = 1.64, 95% CI = 1.28 to 2.10) and 12 months follow-up (RR = 1.42, 95% CI = 1.14 to 1.76)

2 trials reported:

A significant A significant improvement in adherence to antidepressant and oral DM medications were found in the collaborative care group.

Antidepressant adherence was significantly better in the collaborative care group

  • A significant increase in depression remission with CC at 6 months (RR = 1.33, 95% CI = 1.01 to 1.75)
  • A non-significant increase in depression remission with CC at 12 months (RR = 1.20, 95% CI = 0.93 to 1.55)

4 trials reported:

  • A significant improvement in adherence to antidepressant medication in the CC group (RR = 1.79, 95% CI = 1.19 to 2.69)

Diabetes Mellitus outcomes

5 trials reported

  • A (non-significant) pooled effect of a reduction in HbA1c in favour of CC (MD = -0.13 95% CI = -0.46 to 0.19).

4 trials reported:

  • A non-significant reduction in HbA1c in the CC group at 6 (MD = -0.06, 95% CI = -0.24 to 0.12) and 12 months (MD= -0.07, 95% CI = -0.28 to 0.13).

2 trials reported:

  • A significant improvement of adherence to oral DM medications associated with CC (RR= 2.18, 95% CI= 1.61 to 2.96)


  • All studies were from the United States where care is often provided through insurance and there is a high prevalence of DM and obesity. Therefore results may not be representative of the rest of the world.
  • For obvious reasons, patients were aware of treatment allocation. This could have introduced some bias.
  • There was heterogeneity between RCTs, although the results of the larger studies were all similar.


The authors concluded that

Collaborative care significantly improved depression and diabetes outcomes, comparing with usual care.

However, the majority of diabetes outcomes were not significant (the confidence intervals around the HbA1c result were not statistically significant, and the point estimates were not clinically significant), so we would disagree with the conclusions drawn here by the reviewers.

This was a largely well conducted and comprehensive summary of the published evidence, but the review was let down by poor reporting which overstates the impact of collaborative care on diabetes outcomes. Having said that, the authors do address some of the commonly encountered problems in this type of research in testing for bias and heterogeneity.
Collaborative care significantly improved depression and diabetes outcomes, comparing with usual care.

Collaborative care significantly improved depression outcomes, compared with usual care

The King’s Fund recently produced a document discussing the problems of co-morbidity of physical and mental health conditions (Naylor, 2012). It identified that health care costs are increased by at least 45% for each person with a long-term condition and co-morbid mental health problem. The extra costs result in part from increased use of Emergency Care, longer inpatient stays, more frequent admission and higher prescribing rates.

This featured article did not explore the economic evaluation of collaborative care versus care as usual in people with DM and depression.

Other studies have indicated that CC for depression is cost effective because of reduced healthcare utilization or improved functioning (Jacob, 2012). The evidence is limited for CC for DM and depression, and is mostly US-based. It would be really interesting to see how this model works in the National Health Service.


Huang Y. et al Collaborative care for patients with depression and diabetes mellitus: a systematic review and meta-analysisBMC Psychiatry 2013, 13:260.

Depression with a chronic physical health problem (CG91). NICE, 2009.

Naylor, C. et al Long-term conditions and mental health: the cost of co-morbidities (PDF). The King’s Fund, 2012.

Jacob, V. et al Economics of collaborative care for management of depressive disorders: a community guide systematic review (PDF).  Am J Prev Med 2012;42(5):539 –549.

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