Of the many things that long-term alcohol addiction can steal -- careers, lives, health, memory -- one of its most heartbreaking tolls is on relationships. Alcoholics, researchers have long known, have a tendency to misread emotional cues, sometimes taking offense when none was intended or failing to pick up on a loved one's sadness, joy, anger or disappointment.
The misunderstandings can result in more drinking, and more deterioration of relationships and lives.
How does alcohol do all that? A new study finds that the brains of long-term alcoholics, even those who have long abstained, often differ from nonalcoholics' in ways that make them poorer judges of facial expressions. In particular, alcoholics register less intensity in the amygdala and hippocampus (collectively known as the limbic system) when observing faces.
For the study, 15 abstinent alcoholics and 15 nonalcoholics looked at pictures of faces and were asked: "How intelligent do you think this person is?" Each face expressed positive, negative or neutral emotions.
Meanwhile, researchers from Massachusetts General Hospital and Boston University peered into their brains using functional Magnetic Resonance Imaging, which tracks brain activity from second to second. The result is published online in the journal Alcoholism: Clinical and Experimental Research.
Nonalcoholics' limbic systems showed strong activity when the photos projected emotion, but were relatively quiet for neutral expressions.
The alcoholics' limbic systems, on the whole, responded no differently whether the faces expressed strong or no emotion.
The participants in the two groups were matched on factors such as age, IQ, education and socioeconomic status. But their brains reacted completely differently when confronted with evidence of anger, joy, sadness or disappointment.
Ksenija Marinkovic, one of the study's authors, cautioned that it left one of researchers' most burning questions unanswered: Did alcoholism blunt emotional sensitivity, or did emotional insensitivity come before the alcoholism?
The idea that alcohol abuse damages the brain makes intuitive sense. But some research suggests instead that a child's cognitive deficits -- especially in the realm of emotional intelligence -- may set off a cascade of events leading to alcoholism.
Past research has shown that the children of alcoholics often exhibit the same deficits in reading emotions. Children of alcoholics are at far greater risk of becoming alcoholics themselves. "It's a chicken-or-egg problem. We just don't know which comes first," said Marinkovic, who now works at UC San Diego.