Medical disorders affect health outcome and general functioning depending on comorbid major depression in the general population

Abstract

Objective

The objective of this study was to compare health-related quality of life (HR-QoL), disability/work productivity, and health care utilization in a variety of medical disorders with and without comorbid major depressive disorder (MDD) in the general population.

Methods

Twelve-month MDD (Composite International Diagnostic Interview) diagnosis was determined among 4181 participants from a community sample. Medical diagnoses (respiratory, cardiovascular, allergic, endocrine/metabolic, gastrointestinal, and neurological diseases) were made after medical examination. HR-QoL was evaluated with the MOS-SF-36. Outpatient doctor visits and disability/work productivity were assessed by self-report.

Results

Comorbid MDD was associated with a lower SF-36 mental summary score in all medical diagnoses and with a lower physical summary score in comorbid allergic and neurological disorders. The number of coexisting medical disorders was strongly related to lower physical and mental summary scores in cases without comorbid depression. The number of outpatient doctor visits increased by 42% when any of the medical disorders without comorbid MDD was present, and comorbid MDD was associated with a further 24–42% increase, depending on the medical disorder. Comorbid MDD was strongly associated with lower full-time working status (37.1% with MDD vs. 51.0% without MDD) and with a significant increase in disability days (45%) in the presence of any medical disorder.

Conclusions

Findings have consequences for diagnostic and treatment procedures, as well as in relation to the importance of the number of medical disorders in future studies.

Introduction

Many previous studies have demonstrated that major depression significantly impairs health-related quality of life (HR-QoL), general functioning, and work productivity, and causes significant individual and economic burden with direct and indirect costs of illness [1], [2], [3], [4], [5]. Epidemiological studies show that depression is associated with substantial work impairment [5], [6], and experimental studies indicate that adequate depression treatment can substantially reduce work impairment [7]. Since major depression shows a consistent prevalence of about 15% in general hospital patients [8] and is associated with increased somatic symptoms, morbidity, mortality, health care utilization, and costs in individuals with comorbid medical disorders [9], [10], [11], [12], [13], it is recognized as an important and frequent comorbid condition in medically ill patients [9]. The effects of untreated major depression on general functioning are at least equal to those of many somatic conditions, including low-back pain, arthritis, diabetes, and cardiac disease [14].

Available knowledge on the association of depression, medical comorbidity, HR-QoL, health care utilization, and disability/work productivity largely relies on clinical studies with selection bias for certain medical conditions, medical disciplines, and age groups. Most of these studies investigated either patients of a certain age group exhibiting a higher prevalence of medical conditions (e.g., elderly patients) or patients with specific medical conditions (e.g., heart failure, renal diseases, and asthma) [10], [11], [13], [15], [16]. These clinical studies may lack representativeness and generalizability, as opposed to studies in the general population. Interestingly, studies estimating loss of work productivity due to depression have not yet been carried out in relation to comorbid medical disorders [6], [17]. However, the few general population studies on the outcome of comorbidity between medical conditions and depression are limited by the self-reported assessment of medical conditions without further medical verification and do not relate work productivity in depression to medical disorders at the general population level [18], [19], [20], [21].

The aim of this study is to compare HR-QoL, disability/work productivity, and health care utilization in a variety of medical disorders with and without comorbid major depressive disorder (MDD) in the general population. The paper addresses the following specific aims. First, we analyze the effects of various entities of medical disorders with and without MDD on HR-QoL expressed by the physical and the mental summary scores of the SF-36. Second, we examine the impact of the quantity of medical disorders on physical and mental HR-QoL among subjects with and without comorbid MDD. Third, we investigate the effect of MDD on the utilization of outpatient doctor visits, depending on specific entities of comorbid medical diseases. Fourth, we explore the effect of MDD on disability among subjects in the workforce compared to those currently not belonging to the workforce in relation to specific entities of comorbid medical disorders.