Early marijuana use is associated with abnormal brain function

10th Oct 2016

A new study has discovered that early use of marijuana may result in abnormal brain function and lower IQ. Previous studies have found that frequent users of marijuana are at higher risk for cognitive dysfunction and psychiatric illnesses, like depression.

The study looked at four groups of people; depressed using marijuana, depressed not using marijuana, non-depressed using marijuana and non-depressed not using marijuana. The participants were later spilt into early use (before 17), later users and non-users of marijuana. All subjects underwent psychiatric, cognitive, IQ testing and brain scanning.

The results found no evidence that marijuana use improved depressive symptoms. In addition, they showed differences in brain function among the four groups in areas of the brain that relate to reward-processing and motor control. Those who used marijuana from a young age, were found to have highly abnormal brain function in areas related to visuo-spatial processing, memory, self-referential activity and reward processing. The results also showed association with lower IQ scores and early marijuana use.

Using this knowledge, and past research suggesting a genetic role between marijuana use and depression, the researchers collaborated to conduct genetic testing on participants. They found that certain genetic variations of the gene that produces brain derived neurotropic factor (BDNF) was found in a greater proportion in early age users. BDNF is involved in brain development and memory. This finding suggests genetic variation may predispose youth to early marijuana use. However, further research is needed as the sample was only small.

To view the full article, please visit Wiley online library