Marijuana Use May Cause Structural Brain Abnormalilities

Marijuana (aka cannabis, pot, etc) is the most commonly used illicit drug in the United States and many other countries of the world. A new study shows that those who use it only for recreational purposes may develop significant structural abnormalities in the brain.

The study, which was published recently in the Journal of Neuroscience, analyzed high-resolution MRI scans of the brain of young adult students.

An MRI scanning machine

Titled "Cannabis Use Is Quantitatively Associated with Nucleus Accumbens and Amygdala Abnormalities in Young Adult Recreational Users", the study involved forty college students, aged between 18 and 25, in the Boston area of the United States.

The study report, explained the rationale behind the study, and indicated three independent analyses of brain morphometry were conducted (see below):

Animal studies show structural changes in brain regions such as the nucleus accumbens after exposure to Δ9-tetrahydrocannabinol, but less is known about cannabis use and brain morphometry in these regions in humans.

We collected high-resolution MRI scans on young adult recreational marijuana users and nonusing controls and conducted three independent analyses of morphometry in these structures: (1) gray matter density using voxel-based morphometry, (2) volume (total brain and regional volumes), and (3) shape (surface morphometry).

Both students who used marijuana for recreational purposes only, and those who did not use it at all were included in the study. The non-users were included as controls.

None of the students used marijuana for medical reasons; however, half of them said they smoked marijuana casually at least once a week while the other half had never used it before.

All the students underwent MRIs to scan parts of the brain long-linked to human motivation, emotions, reward, and addiction.

The scans revealed nothing out of the ordinary among non-pot users. But among pot smokers, the scans showed clear signs of abnormality in terms of shape, size, and structure. What's more the greater the amount of pot smoked, the greater the brain abnormalities.

The study team acknowledged that additional work is needed to confirm the findings. Nevertheless they argued that their brain-imaging effort raises some troubling questions about the safety of recreational pot.

Some proponents of changes in marijuana laws say marijauana does carry some risks, as does alcohol, and advocate its responsible use among adults and restricted use among young people.

Finally, the study concluded that:

These data suggest that marijuana exposure, even in young recreational users, is associated with exposure-dependent alterations of the neural matrix of core reward structures and is consistent with animal studies of changes in dendritic arborization.

These findings ought to be taken seriously in the light of recent laws allowing legality of 'pot-smoking' in some states of the United States.

References:
1). JM Gilman, JK Kuster et al. Cannabis Use Is Quantitatively Associated with Nucleus Accumbens and Amygdala Abnormalities in Young Adult Recreational Users - The Journal of Neroscience. Downloaded on 16th April, 2014. Available online at http://www.jneurosci.org/content/34/16/5529.abstract.
2). MedlinePlus: Recreational Marijuana Use - . Downloaded on 16th April, 2014. Available online at http://www.nlm.nih.gov/medlineplus/videos/news/Pot_Brain_041814_1.html.