Sleep deprivation as a diagnostic instrument

A 59-year-old man with chronic treatment-resistant depression developed severe cognitive impairment. The severity of depression and the mode of presentation led to difficulty in diagnosis between a dementing disorder and a depressive illness. The diagnostic conundrum was resolved by the use of sleep deprivation (SD), which demonstrated clear subjective and objective improvements in his condition. These changes were quantified by a range of psychometric tests, which showed that initial deficits in cognitive performance improved temporarily after SD, and these improvements were maintained after effective treatment of the depression with electroconvulsive therapy.