Is Pot Safe?

Long-term effects on the brain studied

By Colin Allen, published on July 1, 2003 - last reviewed on January 23, 2015

The medical debate over pot continues. Long-term use of marijuana
causes only minimal permanent damage to neurocognitive functioning.
Researchers at the University of California at San Diego (UCSD) found
among habitual users, the central nervous system suffered only minor
problems of recollection and learning.

The UCSD analysis, published in the
Journal of the International Neuropsychological
Society
, is a synthesis of 15 research studies on the matter.
In total, 704 long-term users and 484 non-users were tested for
neurocognitive performance including reaction time, attention, motor
skills and short-term memory.

Study author Igor Grant, M.D., a professor of psychiatry at UCSD,
found little damage in the brain of users. However, users did have
selective memory lapses and trouble with learning. He notes that these
defects were minor.

While these difficulties could be attributed to alcohol and other
drug use, limited information about other drug use by subjects. The
researchers were also unable to access how psychological issues, such as
depression and personality disorders, factor into marijuana use.

If used for a short period under supervised conditions, researchers
argue that marijuana may be safe for the treatment of certain diseases,
such as cancer and AIDS. The study was funded by the Center for Medical
Cannabis Research, a state supported research center that tests the
usefulness of marijuana.