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ORIGINAL ARTICLES |
From the Regenstrief Institute and the Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana (M.J.B., G.J.E., T.W.C., K.K.); Eli Lilly and Co., Indianapolis, Indiana (R.L.R.); Rand Health, Arlington, Virginia (T.W.C.); and Galt Associates Adjunct and the University of North Carolina at Chapel Hill, Chapel Hill, North Carolina (P.E.S.).
Matthew J. Bair, MD, Regenstrief Institute, Inc., RG-6, 1050 Wishard Blvd., Indianapolis, IN 46202. E-mail: mbair{at}regenstrief.org
| ABSTRACT |
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METHODS: We analyzed data from the ARTIST study, a randomized controlled trial with naturalistic follow-up conducted in 37 primary care clinics. Participants were 573 clinically depressed patients randomized to one of three selective serotonin reuptake inhibitor (SSRI) antidepressants: fluoxetine, paroxetine, or sertraline. Depression as assessed by the Symptom Checklist-20 (SCL-20) was the primary outcome. Secondary outcomes included pain and health-related quality of life.
RESULTS: Pain was reported by more than two thirds of depressed patients at baseline, with the severity of pain mild in 25% of patients, moderate in 30%, and severe in 14%. After 3 months of antidepressant therapy, 24% of patients had a poor depression treatment response (ie, SCL-20 >1.3). Multivariate odds ratios for poor treatment response were 1.5 (95% confidence interval, 0.83.2) for mild pain, 2.0 (1.14.0) for moderate pain, and 4.1 (1.98.8) for severe pain compared with those without pain. Increasing pain severity also had an adverse impact on outcomes in multiple domains of health-related quality of life.
CONCLUSIONS: Pain is present in two thirds of depressed primary care patients begun on antidepressant therapy, and the severity of pain is a strong predictor of poor depression and health-related quality of life outcomes at 3 months. Better recognition, assessment, and treatment of comorbid pain may enhance outcomes of depression therapy.
Key Words: depression, pain, treatment response, primary care.
Abbreviations: ARTIST = A Randomized Trial Investigating SSRI Treatment;; DSM-IV = Diagnostic and Statistical Manual of Mental Disorders, 4th Edition;; HRQL = health-related quality of life;; PHQ-15 = Patient Health Questionnaire somatic symptom severity scale-15;; PRIME-MD = Primary Care Evaluation of Mental Disorders;; SCL-20 = Symptom Checklist-20;; SF-36 = Medical Outcomes Study Short Form-36;; SSRI = selective serotonin reuptake inhibitor.
| INTRODUCTION |
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Patients with depressive disorders often manifest multiple complaints, including an overlapping constellation of emotional and physical symptoms. Physical symptoms (eg, fatigue, insomnia, pain) are more numerous in depressed patients, frequently nonspecific (4,5), often unrelated to a known organic disease process (6), and lead to greater health care utilization. More than 50% of depressed patients report physical complaints only (79), and at least 60% of these complaints are pain-related (1012). Physical symptoms, especially pain, negatively impact recognition of depression (7,8), adherence to medication (13), and adequate therapy (14). As a result, poor depression treatment outcomes are likely (eg, failure to achieve remission). Patients who fail to achieve remission after antidepressant therapy are more likely to suffer residual pain and other physical symptoms compared with the patients that remit (15).
Impairments in social function (16), work function (17), and functional limitations (eg, limited mobility, restricted activity) are exaggerated when depression and pain coexist (18). Furthermore, pain severity and frequency, pain-related functional impairment, and diffuse pain are all associated with more depressive symptoms and more severe depression (19,20). What is not clear is whether patients with depression and pain are less responsive to usual depression management than patients with depression alone. Therefore, we sought to determine whether the presence and severity of baseline pain is associated with poor depression treatment response and health-related quality of life (HRQL) outcomes in a cohort of depressed primary care patients started on SSRI antidepressant therapy.
| METHODS |
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A total of 573 patients from two US primary care research networks, including 37 clinics, were randomized to one of the SSRI antidepressants and evaluated with a battery of depression, social and work functioning, and other HRQL measures. Patients were screened and randomized during a visit to the primary care provider. Computer-assisted telephone interviews were used to collect baseline data and outcomes at 1, 3, 6, and 9 months. Treatment effectiveness was evaluated by the change in depression and psychological measures at each interval and compared across treatment groups. As originally reported, the three SSRIs demonstrated similar effectiveness for depressive symptoms and all HRQL and secondary outcomes over the entire 9 months of the trial (21). For the present article, baseline and 3-month data were analyzed because the focus was on acute-phase (ie, 3-month) depression response as opposed to maintenance treatment response. A total of 504 patients (88% response rate) participated in the 3-month interview, and complete data were available for 501.
Study Measures
The primary outcome was the Symptom Checklist-20 (SCL-20) depression severity scale, a modified subscale of the Hopkins Symptom Checklist and Brief Symptom Inventory. This scale has been used extensively to assess depression outcomes in primary care trials (2225). The 20 items are scored from 0 to 4 and averaged to provide a measure of overall severity from 0 to 4, with higher scores representing more severe depression. The Primary Care Evaluation of Mental Disorders (PRIME-MD) depression module (26) was used to classify patients according to DSM-IV diagnostic subgroups of major depression, dysthymia, and minor depression.
Health-related quality of life outcomes were assessed at baseline and 3-month follow-up by the Medical Outcomes Study Short Form-36 (SF-36) subscales: general health, mental health, physical functioning, role functioningphysical, role functioningemotional, social functioning, and vitality (27). The SF-36 bodily pain subscale was included as an independent variable (instead of an outcome variable) as described below.
Two different pain scales were used. The SF-36 bodily pain subscale provides a composite score ranging from 0 (worst) to 100 (best) health status. The scale consists of two items that were also analyzed separately to address the individual contributions of pain severity and pain interference (ie, how much pain interferes with a persons function at work or at home). The Patient Health Questionnaire somatic symptom severity scale-15 (PHQ-15) measures how much a patient is bothered by 15 different physical symptoms in the last month (28). The PHQ-15 assesses the bothersomeness of five specific pain symptoms: headaches, back pain, limb or joint pain, abdominal pain, and chest pain. The five pain items are summed to provide a composite pain score ranging from 0 to 10, with higher scores indicating more pain. Additionally, each of the pain symptoms were analyzed separately. For analysis purposes, we operationalized pain items from both the SF-36 and the PHQ-15 scales into four pain severity classes. The SF-36 pain severity item responses were categorized as follows: "none" or "very mild" = none, "mild" = mild, "moderate" = moderate, and "severe" or "very severe" = severe pain. PHQ-15 pain scale scores were likewise categorized as none (02), mild (34), moderate (56), and severe (710). Finally, the PHQ-15 also assesses 10 nonpain somatic symptoms, producing a severity score of 0 to 20.
Data Analysis
Data were analyzed using SAS Version 8.2 (SAS Institute, Cary, NC). Multivariate logistic and linear regression modeling were used to assess the independent effect of baseline pain on depression outcomes and, secondarily, HRQL outcomes. To account for possible correlations between patients seen by the same physician or by different physicians in the same clinic, we included physician and clinic as random effects in the models.
For logistic regression, the SCL-20 depression score at 3 months was dichotomized at a cutpoint of 1.3. Patients with scores greater than 1.3 (ie, more severe depression) were defined as poor depression treatment responders. This SCL-20 cutpoint was chosen for three reasons: (1) it is a cutpoint used in a previous primary care depression trial (23); (2) improvements to this level by 3 months represented an average effect size of less than 0.5, a minimal threshold for categorizing health status changes as at least moderate in magnitude (29); and (3) it defined the upper quartile (ie, most severe depression) of patients at 3-month follow-up. For the secondary outcomes, we defined poor HRQL at 3 months as being within the lowest 25th percentile for each domain. Separate models were run for each of the seven SF-36 subscales (excluding bodily pain), with the dependent variable being the specific SF-36 domain and the predictor variable being baseline pain severity as measured by the SF-36 pain severity item and categorized as none, mild, moderate, or severe pain. Odds ratios and 95% confidence intervals were computed while controlling for age, gender, race, initial SSRI assignment (intent to treat with fluoxetine, paroxetine, or sertraline), clinic site, treating physician, nonpain somatic symptom severity, and baseline score of the dependent variable (ie, depression or relevant HRQL domain).
In linear regression models, the dependent variable was the change in SCL-20 depression score from baseline to 3-month follow-up. The predictor variable tested was again baseline SF-36 bodily pain, controlling for the same covariates. Finally, the consistency of our results was examined by creating additional models with the same depression and HRQL outcomes and covariates, but replacing the pain predictor variable with our secondary pain measures: the PHQ-15 pain subscale, the individual SF-36 items of pain severity and pain interference, and the severity of each of the five specific PHQ-15 pain symptoms.
| RESULTS |
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| DISCUSSION |
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Most studies demonstrating a high prevalence of pain symptoms in depressed patients have been conducted in psychiatric or other specialty (eg, pain clinic) settings (3134). However, a few studies situated in primary care settings have reported a 43% to 65% prevalence of pain symptoms in depressed patients (10,35,36). The fact that depressed patients in the ARTIST trial were all judged to have depression severe enough to warrant antidepressant therapy may account for a pain prevalence in the upper range.
In addition, the specific complaints of headache, back pain, abdominal pain, joint pain, and chest pain are frequently endorsed by depressed patients in primary care settings (11,12). The common co-occurrence of depression and pain symptoms is one reason that depression is frequently unrecognized and therefore untreated in primary care. The somatic symptoms often predominate and may distract attention from comorbid depressive symptoms. The new emphasis on pain as the "fifth vital sign" by both the Joint Commission on Accreditation of Healthcare Organizations and the Veterans Health Administration provides an opportunity for better recognizing and understanding the interaction between depression and pain.
Most depression and pain studies have either been cross-sectional or have assessed the adverse impact of comorbid depression on pain outcomes. Relatively fewer studies have addressed the converse: how the presence of pain affects depression response and other secondary outcomes such as functional status, quality of life, and health care costs and utilization. In this regard, several studies by Von Korff et al. (19) have been informative. They found that the presence of as many as five different pain complaints (abdominal pain, headache, back pain, chest pain, and facial pain) is associated with increased depressive symptoms. Similar to our findings, the findings of Von Korff et al. (18) showed that progressive baseline pain severity was associated with more severe depression. Additionally, they demonstrated that increased pain severity was related to more pain-related functional limitations, worse self-rated health, higher unemployment rates, more frequent use of opiate analgesics, and more pain-related doctor visits (at baseline and 1 year follow-up) (18).
A sample of depressed patients experienced pain on more than half the days over a 3-month period and produced 16 days when usual activities were curtailed, 4 days missed from school or work, and at least one visit with a physician or clinical nurse (37). Pain that interferes with daily activities, the number of days in pain (within a 6-month period), and the diffuseness of pain (or number of pain sites) all predict depression severity (20). Depression is associated with failure of back pain to improve at both short-term (7 weeks) and long-term (2 years) follow-up (18,38,39). Additionally, depressive symptoms may improve substantially with a reduction in pain (19).
A few studies have suggested that depressed patients with comorbid chronic low back pain respond just as well (ie, fewer depression symptoms) to antidepressants and cognitive behavioral therapy as depressed patients without back pain (40,41). In contrast, our data from a large randomized clinical trial suggest that baseline pain reduces the benefits of antidepressant therapy at 3 months, both in terms of depression and HRQL outcomes.
Some study limitations warrant mention. For one, we cannot infer a direct cause and effect relation between pain and poor depression outcomes. The ARTIST trial was designed primarily to test the relative effectiveness of three SSRI antidepressants on a variety of depression, HRQL, work, and social functioning outcomes. Our findings regarding the impact of pain on treatment response arise from secondary analysis of this trial and should be confirmed in further studies. Second, we did not measure other variables that may enrich our understanding, such as duration of pain, pain medication use, and which symptoms arose firstdepression or pain.
Nonetheless, our study demonstrates the substantial co-occurrence of depression and pain symptoms and the impact of the latter on depression treatment response. We believe a treatment model that incorporates assessment and treatment of both depression and pain is desirable. However, more research is needed to determine whether alleviation of pain helps the patients depressive symptoms and, likewise, whether relief of depressive symptoms improves pain and its related morbidity or whether a common third factor is related to the severity and response of both pain and depression. In the future, dual therapy trials are needed to assess whether adequate treatment of both depression and pain, rather than an exclusive focus on one or the other, improves patient outcomes.
| ACKNOWLEDGMENTS |
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Received for publication May 14, 2003.
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