Study of Siblings’ Brains Provides Clues to Addiction

A new study of siblings’ brain structure and function may provide clues to addiction. Time reports that the study suggests at least some brain changes seen in addiction are a cause of excessive drug use, not the result.

The study looked at the brain structure and cognitive function of 47 people with addiction, 49 of their siblings who were not addicted, and 50 healthy people who were drug-free and not related to the others in the study. The people who were addicted had been using stimulants such as cocaine or amphetamines for an average of 16 years. A little more than half also were addicted to heroin or prescription painkillers, and one-fourth also had alcoholism. Their siblings had minimal exposure to illicit drugs.

All study participants were tested on their ability to control their impulses, which is a predictor of addiction. They were given a stop-signal task, in which they are told to respond quickly and repeatedly in a specific way, such as pushing a button, and then must suddenly stop the behavior.

The researchers report in Science that both people who were addicted and their siblings demonstrated significantly reduced performance on the task compared with the drug-free, unrelated group. The results suggest that poor impulse control is not a result of drug use, but is something people are born with.

The brain scans found the siblings had similar abnormalities in an area of the brain involved with self-control, and in regions that are involved in inhibiting impulses, the article notes.

In a commentary accompanying the study, Dr. Nora Volkow, Director of the National Institute on Drug Abuse, noted the brain abnormalities seen in the siblings are similar to those seen in the brains of teenagers, who are well known for their impulsive behavior.

Study author Karen Ersche of the University of Cambridge said siblings of drug-addicted people may have inherited a type of protective resilience, such as an easier temperament. “The siblings may have tried drugs, but they never developed the habit,” she said.