Background: Patterns of response and nonresponse in repeated sleep deprivation (SD) are of both clinical and scientific interest; as yet, studies have yielded inconsistent results.
Methods: Eighteen inpatients suffering from a major depression were subjected to a series of six scheduled total sleep deprivations within 3 weeks; 12 of them completed the whole protocol. All were under a constant antidepressant medication with amitriptyline. SD effects were measured using observer and self rating scales.
Results: Each single SD led to a significant improvement. Of the 12 patients who completed the protocol, seven were classified as responders at endpoint (i.e., 1 week after the sixth TSD). The majority of patients exhibited a pattern of responses and nonresponses randomly distributed over time. There was no temporal trend. The initial effect did not predict the average response to the following SDs.
Limitations: One third of patients dropped out before completing the protocol which limits the scope of the study.
Conclusions: Response to a single SD is not generalizable on a series of following SDs in an individual. The mechanism of action of SD does probably not involve mechanisms subjected to habituation or sensitization.