SUNDAY, Aug. 17, 2008 (HealthDay News) -- Taking prescription antidepressants while still highly depressed could impair driving ability, a new study suggests.
"We already know that depression causes concentration problems," said study author Holly J. Dannewitz. "And now it appears that people taking antidepressants who also have relatively higher depression scores fare significantly worse when attempting to perform a computerized simulation of driving."
Dannewitz conducted her research while a graduate student at the University of North Dakota in Grand Forks, where she is currently a psychology resident in a private practice.
She and her colleagues were scheduled to present their findings Sunday the American Psychological Association annual meeting, in Boston.
To gauge the possible impact antidepressants might have on driving performance, the research team asked 60 people to "drive" a computerized version of a car in a program that mimicked real-world conditions.
Approximately half of the participants were taking at least one type of antidepressant, while the other half was taking no medication (other than oral contraceptives in certain instances). Those on antidepressants were screened for current levels of depression and were subsequently categorized as experiencing either low or high depression at the time of the driving test.
Participants had to perform common driving tasks such as braking, steering, and scanning sightlines in response to an unfolding video of car traffic, stop signs, speed limit signs, traffic lights, deer crossings, bicyclists, and even the appearance of helicopters.
People taking antidepressants who were highly depressed registered markedly worse scores on some driving skills than those not taking antidepressants, the team found. This appeared tied to poorer concentration and a weakened ability to react well to situations that divided their attention and relied on memory skills.
These deficits weren't found among those who were taking antidepressants but had low depression scores. In fact, that group was found to execute their driving tasks with a precision equal to that of those not on medication.
Dannewitz said that her future work would involve patients who are diagnosed with clinical depression but not on antidepressants. In this way, her team can determine whether it's the depression, or medications used to treat it, that are at the root of the concentration problems.
"More research needs to be done, of course," she said. "And I wouldn't want to instill fear in drivers. But I think that perhaps individuals who are taking these medications should just be aware of the fact that they may cause concentration problems and impair reaction time."
Dannewitz also stressed that, "this issue is not just a question for drivers, because the cognitive skills needed for driving are also needed for a lot of other skills."
Dr. Bernard Carroll, scientific director of the Pacific Behavioral Research Foundation based in Carmel, California, agreed that it's too early to draw specific conclusions from the study. But he said the findings weren't surprising.
"There is already a very deep literature about subtle impairments of higher cognitive function associated with clinical depression itself, apart from medications," he noted. "I would add that, in any case, medication package inserts routinely warn patients about a whole host of issues when starting a course of psychotropic drugs, including warning against the handling of machinery, driving, or engaging in any occupation in which you can be injured. So, to that extent, this concern isn't new."
For more on antidepressants, head to the American Academy of Family Physicians.