Teenagers respond differently to drugs than adults, and early use may lead to long-lasting effects on brain development, according to new research.

A study presented at the Society for Neuroscience meeting, in San Diego last week, shows people who start using marijuana at a young age have more cognitive shortfalls. Also, the more marijuana a person used in adolescence, the more trouble they had with focus and attention.

"Early onset smokers have a different pattern of brain activity, plus got far fewer correct answers in a row and made way more errors on certain cognitive tests," says study author Staci Gruber, assistant professor of psychiatry at Harvard Medical School.

Her study evaluated 29 non-smokers and 35 chronic marijuana smokers — 20 began smoking pot regularly before age 16 while 15 started smoking after age 16. All were about 22 years old when the study was conducted.

They were asked to perform a card-sorting task where they were shown four cards that differed in color, shape, and number.

While the smokers performed tasks quickly, they did not learn from their errors when corrected — a hallmark that the part of the brain that governs executive function is impaired, says Gruber.

Source: USA Today
http://www.usatoday.com/yourlife/health/medical/pediatrics/2010-11-20-teendrugs22_ST_N.htm?csp=34news