Magnetic Resonance Imaging (MRI) was used to search for any effects on the hippocampus, which is a region of the brain especially involved in memory as well as motion. A group of 22 older, long-term cannabis (marijuana) users with an average lifetime of 20,100 smoking episodes were compared to 26 comparison subjects with no history of marijuana use or dependence.
Those in the marijuana user group displayed no adjusted difference for volumes of gray matter, white matter, cerebrospinal fluid, or left and right hippocampus compared to non-users.
This study states that similar to other literature, there is no suggestion that marijuana use is associated with structural changes in the brain as a whole, nor in the hippocampus in particular.
