Study Finds Marijuana Affects Last 24 Hours

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United Press International

Researchers report that airline pilots who smoke marijuana may have difficulty performing standard landing maneuvers as long as 24 hours later.

Dr. Jerome Yesavage, a Stanford psychiatrist based at the Veterans Administration medical center in Palo Alto, said that the study’s implications “extend beyond the airline industry.”

“These results suggest concern for performance of those entrusted with complex behavioral and cognitive tasks within 24 hours after smoking marijuana. Such results may be applicable to other tasks, such as operating complicated heavy equipment, railway trains and switching procedures.”


Yesavage and his colleagues reported their findings in an article in a recent issue of the American Journal of Psychiatry.

Yesavage said the study involved 10 experienced private airplane pilots who carried out landing maneuvers in a computerized flight simulation laboratory at the medical center.

Yesavage said the pilots, all experienced marijuana smokers, were tested at intervals of 1 hour, 4 hours and 24 hours after smoking marijuana.

The research team found “significant impairments in a variety of landing tasks compared to the pilots’ base-line, pre-pot performance,” he said. “Particularly striking was the finding that impairments persisted even at 24 hours.

“The pilots tended to increase the size and frequency of their manipulations of the ailerons--the moveable wing parts that provide side-to-side control of the plane--and the elevators, which provide vertical control.