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UI researchers study link between steroids, aggressive driving

IOWA CITY, Iowa -- Though anabolic steroids are known to produce aggressive behavior, a University of Iowa study shows that the drugs do not necessarily cause automobile drivers to take extra risks behind the wheel.

Several case studies have reported excessively risky or hostile driving in steroid users. But using the Iowa Driver Simulator, UI researchers found that a group of test subjects showed no changes in driving behavior after several weeks on low and high dose steroids. Subjects also registered no significant changes on psychological tests measuring aggressive or hostile tendencies.

The driving study is part of a larger UI research project funded by the National Institute of Drug Abuse on the effects of anabolic steroids on behavior and thinking. The drugs are often used by weight lifters and other athletes to increase muscle mass and strength. Results of the driving study were published in the American Journal of Drug and Alcohol Abuse.

"Our study mimicked the ways these drugs are being used on the street," says Dr. Paul Perry, UI professor of psychiatry and pharmacy. Study subjects received weekly steroid injections that equaled one to five times the amount of testosterone produced each week by normal males.

Of 42 healthy men enrolled in the larger study, nine participated in the driving component. All were experienced drivers with no history of psychiatric illness. The driving simulation included eight potentially hazardous or frustrating events, including slow-moving vehicles and a car that suddenly cuts in front of the driver.

Subjects demonstrated no significant increase in risky driving based on measures of speed, braking, distance between cars, lane deviation and other factors. They also showed little change in tests of hostility or aggression.

These findings do not mean that all links between anabolic steroid use and aggressive driving should be dismissed, researchers say. They suggest that increased aggression and its effects on driving may require even higher doses of the drugs.

Perry says that personality traits also may help determine how steroids affect driving. Some researchers have hypothesized that steroid abuse is one aspect of a pre-existing tendency toward risk-taking. The controlled design of the UI driving study may have screened out subjects predisposed to aggression by eliminating those who used illicit drugs or showed other risk behaviors. Further work is needed to show how steroids impact driving in different personality types.