Series
Constructs of depression and distress in diabetes: time for an appraisal

https://doi.org/10.1016/S2213-8587(15)00135-7Get rights and content

Summary

Depression presents in roughly 20% of people with diabetes worldwide, and adversely affects quality of life and treatment outcomes. The causes of depression in diabetes are poorly understood, but research suggests a bi-directional association, at least for type 2 diabetes. Inconsistent findings regarding prevalence and depression treatment outcomes in patients with diabetes seem partly attributable to inconsistencies in the definition and measurement of depression and in distinguishing it from diabetes-distress, a psychological concept related to depression. We review evidence suggesting that diabetes-distress and depression are correlated and overlapping constructs, but are not interchangeable. Importantly, diabetes-distress seems to mediate the association between depression and glycaemic control. We propose a model to explain the direct and indirect effects of depression and diabetes-distress on glycaemic control. Additionally, using emerging insights from data-driven approaches, we suggest three distinct symptom profiles to define depression in patients with diabetes that could help explain differential associations between depression and metabolic abnormalities, and to tailor interventions for depression. Future research should focus on further refining depression profiles in patients with diabetes, taking into account the natural history of diabetes and depression, clinical characteristics, and diabetes-distress. The assessment of diabetes-distress and depression in research and clinical practice will be essential to identify high-risk patients with different mental health needs.

Introduction

The co-occurrence of depression and diabetes has been recognised as an emerging global challenge.1 Findings of epidemiological studies2, 3, 4 have shown an overall two-fold increased prevalence of depression and anxiety in patients with type 1 and type 2 diabetes compared with the general population worldwide, adversely affecting quality of life and diabetes outcomes.5, 6, 7, 8 The cause of depression in diabetes remains poorly understood. Evidence suggests a bi-directional association, and the two disorders might share common biological determinants.9 Up to now, psychological and pharmacological treatments have been moderately effective in terms of mood repair, and yield mixed results with regard to enhancing diabetes self-management and normalising blood glucose concentrations.10, 11, 12 As noted at the 2012 National Institute of Diabetes and Digestive and Kidney (NIDDK) conference on diabetes and depression,13 the heterogeneity and inconsistency in reported prevalence and treatment outcomes are at least partly attributable to variability of measurement and use of terminology. Similarly, Fisher and colleagues14 note a “confusing tale of depression and distress” and a failure to define and measure depression in diabetes in a consistent manner. This imprecision could explain the inconsistent and sometimes contradictory findings regarding the link between depression, self-management behaviours, and glycaemic control.

Uncertainties about the construct of depression in diabetes reflect the continuing discussion in psychiatry about the definition of depression and psychiatric classification according to the Diagnostic and Statistical Manual of Mental Disorders (DSM).15 Confusion about concepts of depression and distress is a barrier for cross-disciplinary collaboration in depression research. It seems timely to critically appraise the constructs of depression and distress in diabetes, with the aim to conduct further research in the field and provide guidance for clinical management of comorbid depression. In this Series paper, we focus first on the delineation of depression and the related psychological concepts of distress and diabetes-distress. Second, we focus on the appraisal of the recorded heterogeneity in depression-symptom profiles, and the consequential need for more personalised management of depression in patients with diabetes.

Key messages

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    Comorbid depression and psychological distress present more frequently in people with type 1 and type 2 diabetes than in the general population

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    Depression is a heterogeneous construct, defined on the basis of the presence, severity, and duration of specific symptoms

  • •

    The cause of depression in diabetes is still poorly understood, but partly explained by psychological distress due to the burden of living with a demanding chronic disease

  • •

    Diabetes-distress reflects the person's emotional response to the burden of living with a largely self-managed chronic disease and its debilitating complications

  • •

    Depression and diabetes-distress partly overlap but are not interchangeable constructs

  • •

    Both depression and diabetes-distress are linked to poor adherence and poor glycaemic outcomes, but the underlying pathways can differ

  • •

    Data-driven research in depression has generated different homogeneous symptom clusters that associate with different behaviours and metabolic parameters

  • •

    Three distinct depression profiles have emerged from research that hold promise for more targeted depression treatments: the metabolic, the chronodysregulated, and the anxious depressed

  • •

    Future research should aim to further our understanding of specific depression profiles and changing needs of patients with diabetes to enable more tailored and effective treatments

Section snippets

Depression: a heterogeneous construct

According to the tenth revision of the International Classification of Diseases (ICD-10)16 and the American Psychiatric Association Diagnostic and Statistical Manual of Mental Disorders, fifth edition (DSM-5),17 depression is a mood disorder defined not by cause but as a syndromal diagnosis, made on the basis of several symptoms and the extent of functional deterioration associated with these symptoms. The syndrome encompasses a set of disturbances at the level of emotions (ie, mood symptoms

Epidemiology of major depression

Depression is a common mental disorder. WHO estimated that the 12-month prevalence of mood disorders (including different subtypes of depression) in developed countries was between 3·1% (Japan) and 9·6% (USA).20 Lifetime prevalence estimates for depression are as high as 21%,21 with a preponderance in women. Depression affects both the individual's personal life and society. The estimated lifetime prevalence of suicide in patients with depression is between 2% (outpatients) and 6% (inpatients).

Epidemiology of comorbid depression in diabetes

Depression is twice as common in people with type 1 and type 2 diabetes as in the general population, affecting 10–20% of adults with diabetes.2 Prevalence is higher when depression is assessed by self-report rather than clinical diagnosis. There is no indication that prevalence estimates of depression in diabetes, assessed by either self-report or clinical interview, are inflated by a preponderance of somatic symptoms related to the diabetes or poor glucose control.30, 31

The co-occurrence of

Definition

The term distress was introduced in the early 1970s by the Hungarian physiologist Hans Selye to distinguish between stress initiated by negative, unpleasant stressors and positive stress (eustress).39 Psychological distress is conceptualised as a continuous variable (state measure) that can vary in response to different stressful situations and was defined by Ridner as “the unique discomforting, emotional state experienced by an individual in response to a specific stressor or demand that

Associations between depression and diabetes-distress

In view of the conceptual overlap between psychological distress and depression, unsurprisingly, measures of diabetes-distress show moderate54 to strong55, 56, 57, 58 positive correlations with self-report measures of depression. However, a large part of the variance in diabetes-distress remains unexplained, suggesting that one construct cannot be replaced by the other without loss of information (table). Indeed, factor analysis of data from a cross-sectional study (n=320) in patients with type

Depression, diabetes-distress, and self-care behaviours

Clinical data suggest that depressive symptoms in diabetes are a barrier for treatment adherence. However, the association between depression and treatment adherence does not seem to be a simple linear association. Results of a meta-analysis by Gonzalez and colleagues7 showed a moderate to weak association between depression and self-care behaviour (overall r=0·21), and showed that different self-care domains (eg, diet, physical activity and medication adherence) were differently affected.

Depression, diabetes-distress, and glycaemic control

A meta-analysis of 24 studies by Lustman and colleagues64 showed that depression in diabetes was associated with significantly worse glycaemic control, although the effect size (r=0·17) was small. For depression diagnosed by a standardised clinical interview, the effect size was larger (r=0·28), suggesting that depression severity might affect the risk for hyperglycaemia; the mechanism underlying this association is unknown. Diabetes-distress was not accounted for in this meta-analysis. Both

Emerging insights from data-driven depression research

One of the leading questions in psychiatric epidemiology is whether it is justified to use symptom sum-scores and thresholds as the basis for diagnosing depression.70 This debate is fuelled by divergent results from the specialties of biology, neuroimaging, and genetics,71 questioning the assumption that depression is one disorder. Over the years, investigators have tried to identify meaningful symptom profiles of depression that could have clinical implications. Definition of more homogeneous

Implications for research and practice

Depression is prevalent in people with type 1 or type 2 diabetes, adversely affecting their quality of life and medical outcomes7, 8, 92, 93 and is thus a priority for diabetes clinicians, mental health professionals, and researchers.13 Depression is a heterogeneous construct and defining more homogeneous profiles of depression can be expected to lead to more personalised treatment and improved outcomes. We have proposed three depression profiles: a metabolic-atypical profile, a

Search strategy and selection criteria

We searched Medline and PubMed with combined terms for “diabetes”, “depression”, and “stress” for articles published between Jan 1, 1988, and Aug 31, 2014, written in English or German. Reference lists of original studies, narrative reviews, and previous systematic reviews and meta-analyses were also included. We reviewed titles and abstracts from resulting publications to select studies that reported data for both depression and diabetes-distress. Because our aim was a narrative rather than a

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