Cocaine affects males and females differently, according to a new study by researchers at Wake Forest University.

The researchers exposed monkeys to cocaine while they were in the womb. As adults, the males had poor impulse control, a problem not seen in the females.

A news release from the school said the finding could lead to a better understanding of how drugs affect people.

"We're looking for ways to predict which individuals are going to take drugs during their lives," said Lindsey Hamilton, a graduate student who led the study. "It was particularly interesting, however, that this effect was only seen in the males. Something is either protecting the females from the effects of the cocaine exposure in the womb or making the males more susceptible to the lasting effects."

To test their impulse control, the monkeys were given a choice between a lever that gave one banana pellet immediately or one that gave several pellets after a few minutes.

She said the male monkeys who were exposed to cocaine before birth had "no patience or impulse control whatsoever," especially compared to monkeys raised in similar conditions who were not exposed to cocaine.

In further testing, Hamilton said, it appears that the male monkeys exposed to cocaine in utero are more likely to self-administer the drug, even in low doses, than controls. Again, the difference was not observed in the female monkeys.

The study was presented at the annual Society for Neuroscience meeting in Chicago.