A method for analyzing biological rhythms in healthy subjects and depressed patients.

Rectal temperature rhythms of healthy subjects and patients with depression were fitted to a waveform having cosine components of periods 8, 12, and 24 hours using the least squares method. The nadir was then used as an index of phase. The results suggest that this method gives more exact data than the conventional method of analyzing biological rhythms, which uses a least squares fit to a single, 24-hour-period cosine waveform.