New research from McLean Hospital neuroscientists has revealed that being bullied can have long-term, dramatic effects on sleep, 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."
It is well known that high levels of stress and anxiety can trigger psychiatric illnesses, including depression and PTSD, whereby sleep is frequently affected.
Some people with stress disorders sleep less than normal, while others sleep more than normal or have more frequent bouts of sleep and wakefulness.
According to Science Daily, "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 study revealed that mice who had been bullied showed many more bouts of paradoxical sleep, resembling the type of sleep disruptions often seen in people with depression. Bullied mice also showed a flattening of body temperature fluctuations, which is also an effect seen in people with depression.
What does this mean?
"Both the sleep and body temperature changes persisted in the smaller mice after they were removed from the physically and emotionally threatening environment, suggesting that they had developed symptoms that look very much like those seen in people with long-term depression," said Carlezon.
"These effects were reduced, however, in terms of both intensity and duration, if the mice had been treated with a kappa-opioid receptor antagonist, a drug that blocks the activity of one of the brain's own opioid systems."
"This study exemplifies how measuring the same types of endpoints in laboratory animals and humans might hasten the pace of advances in psychiatry research. If we can knock out stress with new treatments, we might be able to prevent some forms of mental illness."
