Cannabis use may lower brain volume

Participants were assessed with MRI scans at baseline and two-year follow-up and asked about their use of illicit drugs, including cannabis, in the period between scans. 

Of the 57 participants, 25 had used cannabis between the two assessments, and among this group of users there was a reduction in thalamic volume with significant loss on the left side of the thalamus, and “highly significant” loss on the right. No volume loss was found in the group that hadn’t used cannabis.

Br J Psychiatry 2011; 199:386-90