Updated

Friends don't let friends ... drive under the influence of antidepressants?

A study presented Sunday at the Convention of the American Psychological Association in Boston found that people who are depressed and taking prescription antidepressants drive poorly compared to people who are not taking medication.

Researchers at the University of North Dakota measured the driving skills of 60 people, some of whom were not medicated, some who were on antidepressants but were not depressed, and some who were both depressed and taking depression medication. They found that depression, driving and antidepressants don't mix.

The findings are of concern because Americans' use of antidepressant drugs, like Prozac, Paxil and Zoloft, has nearly tripled in the past decade, said researchers, citing government statistics. One in 10 women in the U.S. currently takes an antidepressant, according to the study.

"Individuals taking antidepressants should be aware of the possible cognitive effects as (they) may affect performance in social, academic and work settings, as well as driving abilities," the researchers wrote. "However, it appears that mood is correlated with cognitive performance, more so than medication use."

For the study, researchers had participants make a series of driving decisions, such as reacting to brake lights, stop signs or traffic signals while distracted by speed limit signs, pylons, animals, other cars, helicopters or bicyclists. Steering, concentration and scanning were tested.

Thirty-one of the participants were taking at least one type of antidepressant while 29 control group members were taking no medication with the exception of oral contraceptives in some cases.

The group taking antidepressants was further divided according to how high or low they rated on a test measuring depression.

The group that was both depressed and taking antidepressants performed significantly worse than the control group on several of the performance tasks. Participants who were taking antidepressants and scored in the normal range on the depression test performed no differently than the non-medicated individuals, researchers said.