Brief report
Predicting recovery from episodes of major depression

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Abstract

Background

This study examined psychosocial functioning as a predictor of recovery from episodes of unipolar major depression.

Methods

231 subjects diagnosed with major depressive disorder according to Research Diagnostic Criteria were prospectively followed for up to 20 years as part of the NIMH Collaborative Depression Study. The association between psychosocial functioning and recovery from episodes of unipolar major depression was analyzed with a mixed-effects logistic regression model which controlled for cumulative morbidity, defined as the amount of time ill with major depression during prospective follow-up. Recovery was defined as at least eight consecutive weeks with either no symptoms of major depression, or only one or two symptoms at a mild level of severity.

Results

In the mixed-effects model, a one standard deviation increase in psychosocial impairment was significantly associated with a 22% decrease in the likelihood of subsequent recovery from an episode of major depression (OR = 0.78, 95% CI: 0.74–0.82, Z =  3.17, p < 0.002). Also, a one standard deviation increase in cumulative morbidity was significantly associated with a 61% decrease in the probability of recovery (OR = 0.3899, 95% CI: 0.3894-0.3903, Z =  7.21, p < 0.001).

Limitations

The generalizability of the study is limited in so far as subjects were recruited as they sought treatment at academic medical centers. The analyses examined the relationship between psychosocial functioning and recovery from major depression, and did not include episodes of minor depression. Furthermore, this was an observational study and the investigators did not control treatment.

Conclusions

Assessment of psychosocial impairment may help identify patients less likely to recover from an episode of major depression.

Introduction

Patients suffering from an episode of major depressive disorder often want to know when they will recover. Clinicians and researchers are also interested in prognosis, as it has implications for treatment, is part of psychoeducation, and may help delineate different subtypes of depression. Information about prognosis assumes even more importance, given that unipolar major depression is the single most common psychiatric disorder in the U.S. adult population, with a lifetime prevalence of 16.6% (Kessler et al., 2005).

There currently are no markers or diagnostic tests to help clinicians determine when a patient will recover from an episode of major depression. Although it is known that the median length of major depressive episodes is approximately 20 weeks, duration of illness is highly variable from one patient to another, and for any individual patient, duration of illness varies considerably from one recurrent episode to the next (Solomon et al., 1997). This lack of certainty limits clinical decision-making, and leaves patients and family members wondering what will happen and what they should do.

In response to the need for more information about prognosis, investigators have examined a multitude of variables for their association with faster or slower rates of recovery from episodes of major depression. Unfortunately, no sociodemographic, clinical, biological, or psychosocial functioning variable has been established as a consistent predictor of recovery across the numerous studies that have been conducted. The most that can be said is that sociodemographic variables do not predict the likelihood of recovery, including age at study intake, sex, marital status, and socioeconomic status (Solomon et al., 1997).

For many variables that have been examined, the inconsistent results between different studies are at least partly due to methodological differences. One common methodological problem is that studies of predictors examine recovery from only one episode of major depression. It is clear, however, that major depressive disorder is usually a recurring illness (Solomon et al., 1997) and studying subjects for only a single episode may yield incomplete results.

The present paper investigates the issue of prognosis by building upon previous work that evaluated overall psychosocial functioning as a predictor of recovery. Previously, the authors found a significant relationship between psychosocial impairment and longer episodes of major depression, over a two-year follow-up period (Leon et al., 1999). The present paper extends that work by 1) increasing the length of follow-up for up to 20 years, 2) accounting for cumulative morbidity over time, defined as the amount of time ill with major depression during prospective follow-up (the reason being that psychosocial impairment may simply be a correlate of cumulative morbidity), and 3) conducting two separate analyses, one using a standard definition of recovery and the other a more rigorous definition.

The data for the present study come from the National Institute of Mental Health- Collaborative Program on the Psychobiology of Depression (Collaborative Depression Study). The Collaborative Depression Study is a prospective, observational, longitudinal program that has investigated course of illness in the mood disorders since 1978, and is well suited to study prognosis. The sample of subjects with major depressive disorder is large, diagnostically homogeneous, and well characterized by standardized diagnostic criteria and standardized assessments for follow-up. Subjects in the Collaborative Depression Study have been prospectively followed for up to 20 years, and assessed repeatedly throughout the follow-up period. Many subjects have suffered multiple episodes of major depression during that time. Based upon our previous finding, we hypothesized that increased psychosocial impairment was significantly related to a decreased probability of recovery from episodes of major depression.

Section snippets

Overview

Subjects with unipolar major depression were regularly assessed during follow-up. Level of psychopathology was rated for each week of the study, and level of psychosocial functioning was rated for the particular month in which the rater interviewed the subject. The investigators examined psychosocial functioning in each subject who was actively ill with an episode of major depression at the time of an assessment (time 1). The investigators then examined whether or not those subjects had

Results

Table 2 displays the sociodemographic and clinical characteristics of the 231 study subjects. Subjects were followed for an average of approximately 14 years (mean = 719 weeks, SD = 300 weeks; median = 860 weeks, range: 74 to 1040 weeks).

For each subject, the mean (SD) number of recoveries from episodes of major depression was 3.1 (SD = 2.6), (median = 2.0, range: 0 to 18). The mean (SD) rating of psychosocial impairment on the Longitudinal Interval Follow-up Evaluation- Range of Impaired Functioning

Discussion

The present results indicate that psychosocial impairment is associated with a decreased probability of recovery from an episode of major depression, above and beyond the decreased probability accounted for by cumulative morbidity. Even when a more rigorous definition of recovery was used – at least eight consecutive weeks with no symptoms of major depressive disorder – the association between psychosocial impairment and a reduced probability of recovery was large and statistically significant.

Role of funding source

Funding for this study was provided by NIMH grant MH25478-29A2. The NIMH had no further role in the design of the study; in the collection, analysis, and interpretation of the data; in the writing of the report; and in the decision to submit the paper for publication.

Conflict of interest

Dr. Solomon has served as an investigator for research funded by the National Institute of Mental Health, the National Institute of Neurological Disorders and Stroke, Janssen Pharmaceutica, Wyeth-Ayerst Laboratories, and Merck; as a consultant to Solvay Pharmaceuticals, Shire, and Novartis; and on the lecture bureaus of AstraZeneca, Pfizer, GlaxoSmithKline, and Shire.

Dr. Leon has served as an investigator for research funded by the National Institute of Mental Health, the National Institute of

Acknowledgements

This study was conducted with the current participation of the following investigators: M.B. Keller, M.D. (Chairperson, Providence, RI); W. Coryell, M.D. (Co-Chairperson, Iowa City, IA); D.A. Solomon, M.D. (Providence, RI); W. Scheftner, M.D. (Chicago, IL); J. Endicott, Ph.D., A.C. Leon, Ph.D., and J. Loth, M.S.W. (New York, NY); and J. Rice, Ph.D., (St. Louis, MO). Other current contributors include H.S. Akiskal, M.D., J. Fawcett, M.D., L.L. Judd, M.D., P.W. Lavori, Ph.D., J.D. Maser, Ph.D.,

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