In "Darkness Visible," William Styron explores the connection between disruptions in circadian rhythms and depression. He suggests that alterations in our metabolic and glandular cycles play a significant role in the development of depressive symptoms, indicating that these rhythms are crucial to our daily functioning. This relationship helps explain why conditions like severe insomnia frequently accompany depression, further complicating the mental state of those affected.

Styron also notes that the experience of depression often follows a discernible pattern, marked by alternating phases of extreme distress and temporary relief. This cyclical nature of emotional turmoil reflects how closely tied our mental health is to our biological clock, emphasizing the importance of maintaining a stable routine for overall well-being.