AMHERST, Mass. — It's well known that alcohol consumption is an age-old method for coping with stress. But surprising? research led by the University of Massachusetts Amherst found that, when such self-medication begins in early adulthood, negative cognitive effects start to show up in middle-age—even after long periods of total abstinence.
These effects include a decreased ability to cope with changing situations, an increased likelihood to drink when stressed and the kinds of cognitive decline associated with dementia and Alzheimer's disease. The new research, published recently in the journal Alcohol Clinical and Experimental Research , helps us understand how alcohol rewires the brain's circuitry and can help suggest new approaches for helping people adapt to the long-term effects of alcohol use.
Researchers have long known that stress and alcohol have a mutually reinforcing relationship: alcohol can help take the edge off stressful situations, but in so doing it can decrease the brain's ability to manage stress on its own, meaning one has to keep drinking, and drinking more, in order to relieve stress from a bad day. At the same time, the more one drinks the more stress can accrue from increasingly poor decision making. It can be a vicious cycle that gets harder to break the more the brain's circuitry changes. But what about the long-term effects of stress and alcohol?
"My lab studies the neurocircuitry that underlies how we make decisions," says Elena Vazey , associate professor of biology at UMass Amherst and the paper's senior author. "We all know that drinking can often lead to poor decision-making, but we wondered how early adulthood drinking combined with stress affects that circuitry, especially as we grow older. If we can figure out how alcohol and stress change the brain's circuitry, then we can help figure out how best to help people."
In a line of research supported by the National Institute on Alcohol Abuse and Alcoholism (NIAAA), Vazey and her colleagues worked with mice, whose brain circuitry is similar to that of humans, and discovered that there's something especially potent about the alcohol-and-stress combination when it comes to effects on the brain. Neither alcohol alone nor stress alone do the same damage as the alcohol-stress cocktail.
Furthermore, those who drink heavily to cope with stress as young adults are more likely to fall back on alcohol as a coping mechanism in middle age, even after prolonged teetotaling, suggesting that alcohol and stress can produce a long-lasting rewiring of the brain.
Once middle-age sets in, it appears that a history of stress and alcohol don't have all that much effect on one's ability to learn compared to light drinkers. Instead, flexibility—one's ability to think on one's feet and adapt to new and challenging situations—is markedly reduced.
"Middle age is when problems start to add up," says Vazey. "We know that alcohol is a risk factor for early cognitive decline, and we saw that that this alcohol-stress combination creates the kind of trouble adapting to changing situations that also happens in the early stages of dementia."
But why does this happen? Seeking an answer, the team looked at the part of the brainstem called that locus coeruleus (LC) that is responsible for adaptive decision making in both mice and humans.
The first thing they discovered is how an alcohol-soaked LC responds to stress. In a sober brain, the LC gets activated by stress and then is able to turn itself off when the stress subsides. But in a brain that has been exposed to a history of stress and alcohol, the LC loses the molecular machinery needed to turn itself off, impairing its ability to guide decision making.
The team also found that the LC showed marked signs of oxidative stress, which is a disease marker normally seen in the brains of Alzheimer's patients. Oxidative stress is bad for cells and physiological systems in general. Even after extended abstinence, the middle-aged brains of formerly hard-drinking mice were unable to repair themselves.
"The brain can really struggle to recover from a history of chronic stress and drinking in early adulthood" says Vazey. "We think that the oxidative damage might be one of the things that keeps the heavy drinking going, that can lead to someone going back to alcohol even after long-term abstinence. It's these persistent changes in the brain that also impair decision making and lead to the kinds of early cognitive decline associated with dementia and Alzheimer's. The brain's wiring system is damaged, which means quitting drinking or making better decisions isn't a matter of willpower. After a history of stress and drinking, the brain simply works differently, and our treatment strategies need to able to address these long-lasting differences."
