Researchers at the Rockefeller University in New York found that the anxiety that can result from being teased or being treated poorly is organically based, meaning it arises from physical changes in the brain. “Just as alcohol affects your liver, stress affects your brain,” lead researcher Yoav Litvin was quoted as saying by LiveScience.

The researchers carried out experiments on mice, which are thought to have roughly similar responses to stress as humans, and designed a situation to make the animals feel humiliated.

They placed a small, young test mouse in the cage of a bigger, older mouse. Due to the instinctive territoriality of mice, a fight always ensued, which the newcomer always lost.
The fights were rarely vicious, but the younger mouse quickly understood he was lower down on the social totem pole. The experiment caused more psychological stress then physical harm. The same mouse was subjected to 10 different cages on 10 different days, and was knocked around by the cage’s resident bully each time.

Then the researchers examined each mouse’s brain, looking at areas associated with emotion and social behaviour, such as the amygdala and the lateral septum, which is located near the middle of the fore brain. In bullied mice, the researchers found, the genes for hormone receptors responsible for making the brain sensitive to certain social stimuli had become more active, leading to the production of additional receptors.

Specifically, the amygdala and lateral septum became more sensitive to vasopressin —a hormone involved in many different social interactions, including male-male aggression.
This extra sensitivity may cause a victim to feel scared even in situations when he is safe, the researchers said.

At the end of the study, it was found that the bullied mice froze and stayed away from new, relatively friendly mice.

Though it is not yet known how long the effects last, the finding suggests that the victims of bullies may find it hard to start friendships due to persistent social anxiety, Litvin said. Studies in animals and humans have previously shown that psychological abuse can have long-lasting consequences.

By giving a specific drug that made their brains less sensitive to vasopressin, the researchers calmed the rats.

“But drugs are not the only way to go,” Litvin said, adding that if the social anxiety is particularly strong, a positive relationship with a therapist may be the first step.