Being Bullied May Dramatically Affect Sleep

“This study exemplifies how measuring the same types of endpoints in laboratory animals and humans might hasten the pace of advances in psychiatry research.” – Dr. William Carlezon

New research from McLean Hospital neuroscientists shows in an animal model that being bullied can have long-term, dramatic effects on sleep and other circadian rhythm-related functions, symptoms that are characteristic of clinical depression and other stress-induced mental illnesses. The researchers, however, also found that it may be possible to mitigate these effects with the use of an experimental class of drugs that can block stress.

“While our study found that some stress-related effects on circadian rhythms are short-lived, others are long-lasting,” said William Carlezon, PhD, chief of the Division of Basic Neuroscience and director of the Behavioral Genetics Laboratory at McLean Hospital and senior author of the study. “Identifying these changes and understanding their meaning is an important step in developing methods to counter the long-lasting effects of traumatic experiences on mental health.”

Stress is known to trigger psychiatric illnesses, including depression and PTSD, and sleep is frequently affected in these conditions. Some people with stress disorders sleep less than normal, while others sleep more than normal or have more frequent bouts of sleep and wakefulness.

To demonstrate the effects of bullying, the researchers used an animal model simulating the physical and emotional stressors involved in human bullying—chronic social defeat stress.

For this procedure, a smaller, younger mouse is paired with a larger, older, and more aggressive mouse. When the smaller mouse is placed into the home cage of the larger mouse, the larger mouse instinctively acts to protect its territory.

In a typical interaction lasting several minutes, the larger mouse chases the smaller mouse, displaying aggressive behavior and emitting warning calls. The interaction ends when the larger mouse pins the smaller mouse to the floor or against a cage wall, establishing dominance by the larger mouse and submission by the smaller mouse.

The mice are then separated and a barrier is placed between them, dividing the home cage in half. A clear and perforated barrier…

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