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Sleep Part 1: Mastering the Master Clock

By John McManamy

In late 2006, I heard Frederick Goodwin MD, former director of the NIMH, speak to a DBSA group in Washington DC.

Managing sleep, he told the gathering, is vital to managing one’s bipolar. He went on to say that it was almost as if sleep were the main disorder and bipolar the downstream effect - or words to that effect.

I have observed a similar pattern. In all my years of attending support groups, I have yet to encounter an individual with a mood disorder who did not have serious problems dealing with sleep.

Earlier that year, Dr Goodwin signed for me a copy of the newly-minted second edition of his definitive book (with Kay Jamison PhD), “Manic-Depressive Illness: Bipolar Disorders and Recurrent Depression.” Chapter 16 is devoted exclusively to “Sleep and Circadian Rhythms.”

The authors make clear that although all of us have the equivalent of an internal 24-hour clock that regulates all manner of biological functions, this clock is programmed to respond to the external environment. The “master circadian clock” is located in the surprachismatic nuclei (SCN) of the anterior hypothalamus, just above the brain stem. The SCN cells react to light and dark input from the retina (via glutamate and other neurotransmitters) and from serotonin-producing neurons projecting from the midbrain.

Sleep and wakefulness are regulated by the interaction of circadian rhythms (process s and process c) paced by the SCN.

To function effectively, say the authors, the SCN must synchronize their 20,000 neurons, mainly via GABA neurotransmitters and the hormone melatonin. In humans, the master clock cycles at intervals slightly longer than 24 hours, relying on external cues (such as light and dark and temperature) to sync with the outside world.

Under normal conditions, circadian rhythms “homeostatically” maintain equilibrium. But these rhythms can be disturbed by long-distance travel, shift work, and other hazards of modern living. When the day is going right, our bodies experience a state of wakefulness characterized by: no melatonin secretion, higher core body temperature, decreasing sleepiness, decreasing EEG theta activity, decreasing REM sleep propensity, and decreasing cortisol levels.

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