A disruption of the circadian cycle—the metabolic and glandular rhythms that are central to our workaday life—seems to be involved in many, if not most, cases of depression; this is why brutal insomnia so often occurs and is most likely why each day's pattern of distress exhibits fairly predictable alternating periods of intensity and relief.

Darkness visible: a memoir of madness (ed. Random House Incorporated, 1990) - ISBN: 9780394588889