6. Marijuana use is associated with immediate, but not lasting changes in the brain.
Animal and human studies indicate that marijuana use during development is associated with long-term and even permanent negative changes in the brain, according to studies reported by NIDA. Link (How Does Marijuana Use Affect Your Brain and Body)
Research providing rats with THC early in life show problems with learning and memory later in life, while other animal research shows changes in the hippocampus portion of the brain which is involved in the formation of memory and learning. In addition, longitudinal human studies link lower cognitive abilities including memory and perhaps IQ, even after quitting marijuana use. The level of impairment appears to depend upon the age of initiation, and level and length of use. In addition, some imaging studies suggest that regular marijuana use in adolescence is associated with altered brain conductivity and reduced brain volume in regions associated with memory, learning and impulse control. A recent review of research published in Biological Psychiatry reported that studies show impaired verbal memory, attention and some executive functions may continue even after long-term abstinence from marijuana use, and associations between poorer cognitive performance and younger age of onset were found. Link: (Biological Psychiatry Journal)