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Although a substantial body of research has now addressed the relation between quality of life (QoL) and nonseasonal depression, few studies have assessed QoL in seasonal affective disorder (SAD). We recently measured perceived levels of QoL in a sample of patients (n = 72) diagnosed with SAD during the winter months (1). Both general (as measured by the Quality of Life Enjoyment and Satisfaction Questionnaire [Q-LES-Q]) and health-related (as measured by the Medical Outcomes Study Short-Form General Health Survey [SF-20]) QoL scores were found to be impaired in the sample, compared with general population norms. For example, patients with SAD showed mean Q-LES-Q scores (range 0 to 100, where higher scores indicate better QoL) of 44%. SAD is characterized by episodes of fall or winter depression, interspersed with periods of hypomania or euthymia during the summer months. It is of interest to know whether patients with SAD experience concomitant improvements in their perceived QoL during the summer months. To answer this question, we reassessed QoL in a subset of our original cohort of patients during the summer months, when they were clinically euthymic. Material and MethodsParticipants were 26 patients aged between 18 and 65 years and enrolled at 2 centres (Vancouver, British Columbia, and Toronto, Ontario) of a multicentre study in Canada. Patients were diagnosed with winter depression according to the Structured Clinical Interview for DSM-IV (SCID) criteria and exhibited winter scores of ≥ 20 on the 17-item Hamilton Depression Rating Scale (HDRS, 2) or a score of ≥ 14 on the 17-item HDRS if the 24-item HDRS was ≥ 23. Exclusion criteria included pregnancy, suicidal risk, a range of DSM-IV diagnoses (such as organic mental disorders, substance misuse, schizophrenia, panic disorder, bulimia, anorexia, posttraumatic stress disorder, and bipolar disorder type I), serious illness, contraindicated medical conditions (such as retinal disease), or contraindicated drug use. Participants were randomized to 8 weeks of treatment with either 1) active light therapy with a fluorescent light box (10 000 lux white light for 30 minutes daily in the morning) plus placebo or 2) placebo light therapy with an identical light box (100 lux white light for 30 minutes daily in the morning) plus active drug (fluoxetine 20 mg daily). At the summer assessment, participants were required to have a Beck Depression Inventory (BDI) score of < 18. We used 2 instruments to assess QoL: the SF-20 (3) and the Q-LES-Q (4). The SF-20 is a brief measure of health-related QoL that assesses 6 dimensions (that is, physical, social and role functioning, mental health status, health perceptions, and bodily pain). The Q-LES-Q is a 93-item measure of overall QoL that has 8 summary scales that reflect major life domains, including physical health, mood, leisure time activities, social relationships, general activities, work, household duties, and school or course work. Participants completed the scales during the winter of 2001–2002 (prior to treatment onset) and during July or August the following summer. The University of British Columbia Clinical Research Ethics Board approved the study. Statistics Summary scores for the SF-20 and Q-LES-Q domains were derived and transformed linearly to a scale of 0 to 100. We compared differences in winter and summer domain scores, using Student’s paired t tests with Bonferroni corrections. ResultsParticipants were 16 women and 10 men (mean age 46 years, SD 12; mean BDI score 5.6, SD 5.4). QoL was significantly better during the summer in 3 out of 6 of the SF-20 domains (Table 1) and 7 out of 8 of the Q-LES-Q domains (Table 2).
DiscussionThe findings of this study indicate that patients with SAD show sizable improvements in their perceived QoL during the summer months. Numerical improvements were apparent in all SF-20 and Q-LES-Q domain scores. Statistically significant improvements occurred in 3 of the 6 SF-20 domains mental health, health perceptions, and social functioning but not in physical functioning, role functioning, and pain. Scores for these latter domains were within normal range during both the winter and summer months. For example, in the Primary Care Evaluation of Mental Disorders (PRIME-MD) 1000 study, SF-20 scores for physical functioning (mean 72, SD 27), role functioning (mean 73, SD 41), and pain (mean 60, SD 28) were generally lower than those obtained in the present study during either season (5). However, striking seasonal variations were apparent in the SF-20 domains more obviously related to mood, such as mental health functioning scores, which increased from mean 39, SD 18, during the winter months to mean 75, SD 16, during the summer months. This compares with mental health functioning scores of mean 73, SD 19, observed in the PRIME-MD 1000. All Q-LES-Q domains were significantly improved during the summer months, with the exception of coursework and occupational functioning, where the sample sizes were smaller. Most of these improvements constituted a greater than 20-point increase in mean Q-LES-Q domains. For example, mood scores increased from mean 52%, SD 17%, to mean 77%, SD 15%. Mean Q-LES-Q scores were 69%, SD 14%, during the summer assessment, compared with 83% reported for a general population sample (personal communication, M Rapaport, March 2002). The results of this study have several implications. First, they indicate that perceived QoL, particularly that relating to emotional and social functioning, is markedly impaired in patients with SAD during the winter months. The degree of impairment is equivalent to or greater than that observed in other psychiatric populations (1). Second, these results may have ramifications for the ongoing debate concerning the diagnostic validity of SAD (6,7). Several studies have now indicated that interepisode functioning and QoL remain impaired in patients with bipolar disorder (see 8 for review) and recurrent nonseasonal depression (for example, 9,10). Our data showing that well-diagnosed patients with SAD can recover their functioning during the summer months provides further evidence that seasonal and nonseasonal depression are distinct depressive subtypes. Notably, this cohort of patients was undergoing systematic treatment for their condition. We are engaged in further research to determine whether untreated patients with SAD exhibit similar improvement in functioning during the summer months and to question whether differential effects on QoL occur for light therapy, compared with pharmacotherapy. Funding and SupportDr Michalak was supported by a Canadian Institutes of Health Research (CIHR)/Wyeth Ayerst Canada Postdoctoral Research Fellowship. This study was supported, in part, by a research grant from the CIHR (MCT-38150). References1. Michalak EE, Tam EM, Manjunath CV, Solomons K, Levitt AJ, Levitan R, and others. Generic and health-related quality of life in patients with seasonal and nonseasonal depression. Psychiatry Res 2004;128:245–51. 2. Hamilton M. Development of a rating scale for primary depressive illness. Br J Soc Clin Psychol 1967;6:278–96. 3. Stewart AL, Hays RD, Ware JE Jr. The MOS Short-Form General Health Survey. Reliability and validity in a patient population. Med Care 1988;26:724–35. 4. Endicott J, Nee J, Harrison W, Blumenthal R. Quality of Life Enjoyment and Satisfaction Questionnaire: a new measure. Psychopharmacol Bull 1993;29:321–6. 5. Linzer M, Spitzer R, Kroenke K, Williams JB, Hahn S, Brody D, and others. Gender, quality of life, and mental disorders in primary care: results from the PRIME-MD 1000 Study. Am J Med 1996;101:526–33. 6. Grof P. Mood disorders—new definitions, treatment directions, and understanding. Can J Psychiatry 2002;47:123–4. 7. Michalak EE, Lam RW. Evidence supports validity of seasonal affective disorder. Can J Psychiatry 2002;47:338. 8. Michalak EE, Yatham LN, Lam RW, Wan DC. Quality of life in bipolar disorder: a review of the literature. Am J Psychiatry. Forthcoming. 9. Rouillon F, Berdeaux G, Bisserbe JC, Warner B, Mesbah M, Smadja C, and others. Prevention of recurrent depressive episodes with milnacipran: consequences on quality of life. J Affect Disord 2000;58:171–80. 10. Hirschfeld RM. Psychological predictors of outcome in depression. In: Bloom FE, Kupfer DJ, editors. Psychopharmacology: the fourth generation of progress. New York: Raven Press; 1994. 11. Stewart AL, Hays RD, Ware JE Jr. The MOS Short-Form General Health Survey. Reliability and validity in a patient population. Med Care 1988;26:724–35. AuthorsManuscript received February 2004, revised, and accepted August 2004. 1. Research Associate, Department of Psychiatry, University of British Columbia, Vancouver, British Columbia. 2. Clinical Associate Professor, Department of Psychiatry, University of British Columbia, Vancouver, British Columbia. 3. Medical Instructor, Department of Psychiatry, University of British Columbia, Vancouver, British Columbia. 4. Associate Professor, Department of Psychiatry, University of Toronto, Toronto, Ontario. 5. Professor, Department of Psychiatry, University of British Columbia, Vancouver, British Columbia. Address for correspondence: Dr EE Michalak, Division of Mood Disorders, Department of Psychiatry, University of British Columbia, 2255 Wesbrook Mall, Vancouver, BC V6T 2A1 e-mail: emichala@interchange.ubc.ca
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