Letters to the Editor
Developmental Alcohol Exposure, Circadian Rhythms, and Mood Disorders
Dear Editor:
Alcohol exposure during rapid brain growth causes cell loss, alters connections between brain regions, and decreases the production of brain chemicals responsible for the communication among neurons (1,2). Thus, it is reasonable to suggest that alcohol may adversely affect the development of the suprachiasmatic nucleus (SCN), the master circadian pacemaker. Adult rats exposed to alcohol during the early postnatal period—a critical period of brain development—exhibited a shortened circadian sleep–wake cycle (1). Other experimental and clinical studies have reported that prenatal exposure to alcohol results in sleep abnormalities (1,3).
Studies suggest that abnormalities in circadian rhythm are involved in the etiopathogenesis of seasonal affective disorder (SAD) (4,5). The phase-delay hypothesis of SAD postulates that some components of circadian rhythm are phase delayed relative to sleep in SAD. The photoperiod hypothesis of SAD suggests that the shortening of the photoperiodic environment during winter months triggers SAD. Some researchers have proposed that the pathophysiology of SAD is related to the changes in strength or precision of circadian rhythms.
Abnormalities of circadian rhythm have also been implicated in the etiopathogenesis of nonseasonal mood disorders (5–7). The temporal distribution of rapid eye movement (REM) sleep earlier in the night in depression patients could be a result of a phase advance of circadian rhythms. Several clinical features of bipolar disorder, such as diurnal mood variation, early morning awakening, and the cyclical pattern of relapse, may be associated with circadian disruption (6). Several types of experiments indicate that alterations in the timing of sleep and wakefulness relative to other circadian rhythms may trigger the onset or offset of episodes of depression and mania (6,7).
Thus, it is reasonable to suggest that developmental alcohol exposure produces abnormalities in circadian rhythms that may contribute to the development of seasonal and nonseasonal mood disorders. Circadian rhythm abnormalities are one of many harmful effects of developmental alcohol exposure.
References
1. Earnest DJ, Chen WJA, West JR. Developmental alcohol and circadian clock function. Alcohol Res Health 2001;25:136–40.
2. Maier SE, Miller JA, West JR. Prenatal binge-like alcohol exposure in the rat results in region-specific deficits in brain growth. Neurotoxicol Teratol 1999;21:285–91.
3. Rosett HL, Snyder P, Sander LW, Lee A, Cook P, Weiner L, and others. Effects of maternal drinking on neonate state regulation. Dev Med Child Neurol 1979;21:464–73.
4. Desan PH, Oren DA. Is seasonal affective disorder a disorder of circadian rhythms? CNS Spectrums 2001;6:487–501.
5. Boivin DB. Circadian clock. In: Partonen T, Magnusson A, editors. Seasonal affective disorder. Practice and research. Oxford (UK): Oxford University Press; 2001. p 247–58.
6. Wehr TA, Sack D, Rosenthal N, Duncan W, Gillin JC. Circadian rhythm disturbances in manic- depressive illness. Federation Proceedings 1983;42:2809–14.
7. Riemann D, Berger M, Voderholzer U. Sleep and depression—results from psychobiological studies: an overview. Biol Psychol 2001;57:67–103.
Leo Sher, MD
New York, New York
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