Monitoring of long-term motor activity in depressed patients.

Wrist motor activity was continuously recorded by a solid-state monitor in 12 patients with major depression throughout their stay in hospital; their clinical state was evaluated using three scales. During the day, activity troughs and immobility peaks occurred before noon and around 1500 hrs. Activity level progressively increased, while the duration of immobility decreased, with clinical improvement. The immobility measurement appeared to be a valuable index of depression and is more sensitive than the activity level, mainly for agitated depressed patients. Immobility episodes during the day could suggest the release of an ultradian sleep-wake rhythm in depression.