CHAPEL HILL, N.C. – Doctors have long recognized a link between alcoholism and anxiety disorders such as post-traumatic stress disorder (PTSD). Those who drink heavily are at increased risk for traumatic events like car accidents and domestic violence, but that only partially explains the connection. New research using mice reveals heavy alcohol use actually rewires brain circuitry, making it harder for alcoholics to recover psychologically following a traumatic experience.
“There’s a whole spectrum to how people react to a traumatic event,” said study author Thomas Kash, PhD, assistant professor of pharmacology at the University of North Carolina School of Medicine. “It’s the recovery that we’re looking at — the ability to say ‘this is not dangerous anymore.’ Basically, our research shows that chronic exposure to alcohol can cause a deficit with regard to how our cognitive brain centers control our emotional brain centers.”
Over the course of a month, the researchers gave one group of mice doses of alcohol equivalent to double the legal driving limit in humans. A second group of mice was given no alcohol. The team then used mild electric shocks to train all the mice to fear the sound of a brief tone.
When the tone was repeatedly played without the accompanying electric shock, the mice with no alcohol exposure gradually stopped fearing it. The mice with chronic alcohol exposure, on the other hand, froze in place each time the tone was played, even long after the electric shocks had stopped.
The pattern is similar to what is seen in patients with PTSD, who have trouble overcoming fear even when they are no longer in a dangerous situation.
The researchers traced the effect to differences in the neural circuitry of the alcohol-exposed mice. Comparing the brains of the mice, researchers noticed nerve cells in the prefrontal cortex of the alcohol-exposed mice actually had a different shape than those of the other mice. In addition, the activity of a key receptor, NMDA, was suppressed in the mice given heavy doses of alcohol.