Thomas Wehr

Who is Thomas Wehr?

Thomas Alvin Wehr, scientist emeritus at the National Institute of Mental Health is a psychiatrist, research scientist, author, and former chief of the Clinical Psychobiology branch at NIMH.

Wehr received his degree in medicine from the University of Louisville School of Medicine in 1969. He subsequently completed his psychiatric residency at Yale School of Medicine and his internship was at Michael Reese Hospital.

In a 1990s study on photoperiodicity in humans, Wehr placed a group of volunteers in an environment in which it was dark for 14 hours each day for a month. The subjects were able to sleep as much as they wanted during the experiment. The first night, the subjects slept an average of 11 hours a night. This was judged as probably repaying a chronic sleep debt. By the fourth week, the subjects slept an average of eight hours a night – but across two separate blocks, not unbroken. First, subjects tended to lie awake for one to two hours and then fall quickly asleep. Onset of sleep was linked to a spike in the hormone melatonin. Melatonin secretion by the brain's pineal gland is triggered by darkness. After an average of three to five hours of sleep, the subjects would awaken and spend an hour or two in quiet wakefulness before a second three- to five-hour sleep period. It was thus suggested that such a biphasic pattern of sleep is the natural or pre-historic tendency for humans.