Using pot as a teen may affect thinking

NEW ORLEANS, April 20 (UPI) -- The primary ingredient in marijuana, if used during adolescence, can affect learning and memory later in life, U.S. researchers said.

Dr. Peter Winsauer of Louisiana State University had found that estrogen -- or, more specifically, having ovaries -- made adult rats exposed for the first time to THC, the primary ingredient in marijuana and hashish, less sensitive to THC's negative effects on tests of learning and memory.

Winsauer said the results indicate that the effects of THC and estrogen are different, depending on age, and, even more important, that THC use during adolescence, a critical period of development, has lasting effects on cognitive processes such as learning and memory.

The researcher said he believes illicit use of THC during adolescence produces persistent changes in the brain that sensitize females to the negative effects of THC later in life.

A group of 12 female rats, 35 days old -- an age equivalent to that of human teenagers about to undergo puberty -- began to be exposed to THC chronically for 40 days. Half had had their ovaries removed when they were 30 days old, half retained their ovaries. The day after the 12 females finished the period of exposure, they underwent an extensive training process consisting of pressing colored keys in a specific sequence in order to obtain food pellets.

The female rats went from a 25 percent error rate to 50 percent error rate, Winsauer told United Press International.

The study was presented at Experimental Biology 2009 as part of the scientific program of the American Society for Pharmacology and Experimental Therapeutics in New Orleans.