Can We Predict Depression in COPD?

The course of chronic obstructive pulmonary disease (COPD) is often complicated by multiple systemic co-morbidities ([1]). Depression, one of these co-morbidities, is often undiagnosed and undertreated. The Word Health Organization Burden of Disease survey estimated that by the year 2020, major depression will rank the second and COPD will rank the sixth cause of disability in the world ([2]). While the point prevalence of depression in a primary care population ranges from 5 to 9%, its prevalence as a major co-morbidity in chronic diseases such as COPD is much higher ([3]). In fact, recent studies report prevalence rates of depressive symptoms in patients with COPD ranging between 28 to 42% ([4], [5], [6], [7]). In a study examining the level of psychological distress, patients with COPD experienced significantly more psychological distress than the general population but significantly less than psychiatric outpatients. However, once patients with COPD reported depressive symptoms, the level of distress became similar to that seen in psychiatric outpatients ([8]).

Depression magnifies the morbidity and worsens the functional and health status of patients with COPD. Most studies reveal that depressive disorders in patients with COPD are often associated with moderate to severe symptoms leading to a reduced functional capability of patients due to neurobiological impairment ([9], [10]). This increases the morbidity and cost of the disease. In one study, subjects with acute exacerbation of COPD who scored highest on a depression scale administered during the exacerbation visit had a higher relapse rate and therefore higher healthcare costs than subjects without depression ([11]). Multiple studies, using different quality of life instruments, have documented that health status in depressed patients with COPD is worse than in the general COPD population ([12], [13], [14], [15], [16], [17]).

In most of these studies, depression along with decreased physical functioning are identified as major contributors to the impaired health status. Moreover, while severe disease is typically associated with a worse health status ([18], [19]), a similar correlation between disease severity and the degree of depression is not well established. It is also unknown whether depression impacts the overall mortality in COPD although the results of a large, prospective, 7-year study suggest that patients with severe symptoms may also have an increase in overall mortality ([20]).

While growing evidence suggests that certain interventions such as pulmonary rehabilitation ([21]) anti-depressants ([22]) and counseling may improve health outcomes, depression in COPD continues to be overlooked by busy practitioners. Further, it is estimated that only one third of patients with COPD who suffer from depressive symptoms receive proper treatment for their condition ([6]). Many factors may play a role in this.

Unfortunately, an element of stigma is still attached to depression in general practice, which may lead to a delay in seeking help by patients or the reluctance of making the diagnosis by their treating physician. Furthermore, data from a multinational interview-based patient study conducted in Europe reveal that physicians often underestimate the psychological impairment experienced by patients during a COPD exacerbation during which the majority of patients report that worsening of their symptoms significantly influenced their mood and over 42% stated that the exacerbation affected their personal relationships ([23]).

Unfortunately, evidence-based guidelines for COPD do not provide an outline for a comprehensive approach to screening, diagnosing and treating depression. Practical screening instruments for depression like the HADS and PRIME-MD are highly validated and have excellent positive predictive value and can be used in the primary care setting.

More detailed questionnaires such as the Becks Depression Inventory II and Symptom Checklist 90–Revised are also useful for evaluating and detecting depression ([8]). Although screening tools are currently available, none has been widely used in the primary care setting or by specialists. Only a few studies thus far have attempted to identify predictors of depression in patients with COPD. Most of these studies suggest that women, current smokers and symptomatic patients (dyspnea) are at higher risk for depression than others ([24], [25], [26], [27]).

In this issue of the Journal, Coultas and colleagues evaluated predictors of depressive symptoms in patients with COPD and their health impact ([28]). Like other studies, this study concluded that depressive symptoms are common among patients with COPD and are associated with an increase in health care utilization. The majority of patients in this study were Caucasian (87.9%), elderly (mean age 69.2 years), had at least one other chronic disease (95%) and belonged to a low socioeconomic class with 70% earning less $20,000 per annum and 89% were unemployed.

While some of these characteristics may limit the generalize ability of the results, this study identified important bio-psycho-social factors (smoking, self-efficacy, illness intrusion, social support) as major determinants of depression in this population. Former smokers and patients with higher confidence in managing breathing difficulty had a lower risk of depressive symptoms. On the other hand, when COPD was perceived as an intrusive entity to ones health, functioning and relationships, the risk of depressive symptoms increased.

The study results suggest that the use of bio-psycho-social predictors for depressive symptoms may increase the detection and is important to be addressed in the management of depression in patients with COPD. Given the high prevalence and impact of depression in patients with COPD, it is important that simple psychiatric screening measures be developed and be widely implemented to detect depression early in the course of this disease. It is also essential that future studies continue to identify predictors and determinants of depression in COPD, the fact that may help clinicians identify patients at risk and thus implement early intervention.