Young adults who smoke marijuana (cannabis) from time to time may experience significant changes in two key areas of the brain, which play an important role in emotions and motivations. This is what is stated by a new U.S. scientific research, which, at the same time, does not lead to any definitive conclusion as to how harmful this substance is in small to moderate quantities.
This is the first study that shows that there may be consequences even for the occasional marijuana users, and as the weekly use increases, the possibility of brain damage is rising. Previous studies only found brain lesions in chronic and frequent users of marijuana (more than 20 cigarettes a week for several consecutive years).
The researchers of the Medical Schools of Harvard and Northwestern universities and the Massachusetts General Hospital, led by Professor of psychiatry Hans Breiter did a comparative analysis of the brains of 20 occasional users of marijuana (who smoked one to five times a week) and 20 non-users, all of whom were men and women aged 18-25 years.
“This study raises serious doubts about the hitherto prevailing perception that occasional marijuana use is not associated with bad consequences. People think they do not run any risk if they smoke a little marijuana to relax if does not create problems at work or at school. But our data suggest other things. Some of the people with brain lesions smoked marijuana to “get high” only once or twice a week,” says Breiter.
The lesion was centered in the nucleus accumbens and amygdala, two vital areas of the brain that regulate emotions and motivation, as well as the development of substance addiction. The scientists identified changes in volume, shape and density of brain tissue in occasional marijuana users. The size of the lesions was directly related to how frequent the use was.
The researchers found something similar to what was already shown by similar studies in animals. The brain that is exposed to marijuana (and, in particular, to the THC substance it contains) creates new neuronal synapses. As more dopamine is released in the brain, the scientists suspect that users tend to get more enjoyment from marijuana compared with other sources of pleasure (food, sex, social contacts, etc.), while they also experience a chronic lack of motivation and lose their interest to achieve their goals.
As said by the lead research professor, bigger studies need to be conducted to confirm what was shown by studies on animals, that’s is that marijuana is an addictive “gateway” to the use of stronger and more devastating drugs. On the other hand, it remains unclear to what extent these brain lesions caused by the use of marijuana are actually harmful to the users over time. Question mark is also on whether the brain lesions are irreversible or can disappear if one stops the use of marijuana.
The researchers pointed out that in our time marijuana has a higher content in psychoactive substance tetrahydrocannabinol. While in the decades of hippies, 60s and 70s, when the content was usually 1% to 3%, now it reaches 5% to 9% and sometimes even more. This makes marijuana more active in the brain and cognitive-emotional functions. The study was published in the «Journal of Neuroscience».