Circadian rhythm disturbances in manic-depressive illness
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Abstract:
Clinical features of manic-depressive illness, such as diurnal variation in mood, early morning awakening, and cyclicity and seasonality of recurrences, have led to speculation that the circadian system may be involved in its pathophysiology. At least three types of circadian rhythm abnormalities have been described in such patients: blunting of circadian rhythms' amplitudes, advanced position (or even nonentrainment) of circadian rhythms' phases, and doubling of the length of the sleep-wake cycle from 24 to 48 h. Several types of experiments indicate that alterations in the timing of sleep and wakefulness relative to other circadian rhythms (i.e., changes in internal phase relationships) may trigger the onset or offset of episodes of depression and mania. Whether drugs used to treat manic-depressive illness act through their effects on the circadian system is currently being investigated. Direct manipulations of the circadian system are also being investigated as new approaches to treatment.
Insights
Manic-depressive illness may involve circadian system dysfunction, with abnormal rhythms potentially triggering mood episodes. Research is exploring treatments targeting these biological rhythms.
Area of Science:
- Neuroscience
- Chronobiology
- Psychiatry
Background:
- Clinical features of manic-depressive illness (bipolar disorder) suggest a role for the circadian system.
- Observed symptoms include diurnal mood variation, early morning awakening, and cyclical/seasonal recurrences.
Purpose of the Study:
- To explore the involvement of the circadian system in the pathophysiology of manic-depressive illness.
- To review described circadian rhythm abnormalities in patients.
- To examine the relationship between circadian timing and mood episode onset/offset.
Main Methods:
- Review of experimental findings and clinical observations related to circadian rhythms in manic-depressive illness.
- Analysis of documented circadian rhythm abnormalities: amplitude blunting, phase advances/nonentrainment, and altered sleep-wake cycle length.
- Investigation into the potential impact of internal phase relationship changes on mood episodes.
Main Results:
- Three main types of circadian rhythm abnormalities are identified in patients: blunted amplitudes, advanced phases (or nonentrainment), and a doubled sleep-wake cycle (48-hour cycles).
- Alterations in the timing of sleep and wakefulness relative to other circadian rhythms may precipitate manic or depressive episodes.
Conclusions:
- The circadian system is strongly implicated in the pathophysiology of manic-depressive illness.
- Further research is investigating the effects of current treatments on the circadian system and exploring direct circadian system manipulations as novel therapeutic strategies.