Letters to the Editor
Evidence Supports Validity of Seasonal Affective Disorder
Dear Editor:
We were surprised to read in a recent editorial that Dr Paul Grof questions
the validity of the diagnosis of seasonal affective disorder (SAD). He
writes that “the evidence for the existence of SAD itself is still missing,
more than 20 years after it was proposed. In clinical course, genetic,
and treatment studies, there is still no convincing justification for the
diagnosis of an independent seasonal illness” (1, p 124). This statement
seems based more on idiosyncratic opinion than on scientific evidence.
First, it is worth clarifying that the DSM-IV classifies SAD as a seasonal
pattern specifier for major depressive disorder (MDD) (2), and hence, it
is regarded as a subtype of depression rather than an independent diagnostic
category. Second, there is ample evidence to demonstrate that seasonal
pattern is a valid specifier for MDD and that light therapy is an effective
treatment for SAD. Since the condition was first described in 1984, nearly
1000 articles have been indexed on Medline under the heading, “seasonal
affective disorder.” Indeed, extensive reviews support an argument that
there is more evidence for the validity of SAD than for many other well-recognised
depressive subtypes, including bipolar II disorder, atypical depression,
and postpartum depression (3,4). SAD and its treatment have also been comprehensively
reviewed and included in Canadian (5), American (6), and international
(7) evidence-based guidelines for the treatment of depressive disorders.
We suggest that it is time to leave behind the argument of whether SAD
is a valid diagnosis and concentrate instead upon determining the pathophysiology
and most effective methods of identifying and treating this prevalent and
disabling subtype of depression.
References
1. Grof P. Mood disorders—New definitions, treatment, directions, and understanding
[editorial]. Can J Psychiatry 2002;47:123–4.
2. American Psychiatric Association. Diagnostic and statistical manual
of mental disorders. 4th ed. Washington (DC): American Psychiatric Association;
1994.
3. Bauer MS, Dunner DL. Validity of seasonal pattern as a modifier for
recurrent mood disorders for DSM-IV. Compr Psychiatry 1993;34:159–70.
4. Enns MW, Levitan RD, Levitt AJ, Dalton EJ, Lam RW. Diagnosis, epidemiology
and pathophysiology. In: Lam RW, Levitt AJ, editors. Canadian consensus
guidelines for the treatment of seasonal affective disorder. Vancouver
(BC): Clinical and Academic Publishing; 1999.
5. Kennedy SH, Lam RW, Cohen NL, Ravindran AV. Clinical guidelines for
the treatment of depressive disorders. IV. Medications and other biological
treatments. Can J Psychiatry 2001;46 Suppl 1:38S–58S.
6. American Psychiatric Association. Practice guidelines for the treatment
of patients with major depressive disorder (revision). Am J Psychiatry
2000;157:1–45.
7. Bauer M, Whybrow PC, Angst J, Versiani M, Moller H-J. World Federation
of Societies of Biological Psychiatry (WFSBP) guidelines for biological
treatment of unipolar depressive disorders, part 1: acute and continuation
treatment of major depressive disorder. World Journal of Biological Psychiatry
2002;3:5–43.
Erin E Michalak, PhD
Raymond W Lam, MD, FRCPC
Vancouver, British Columbia
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