Repost from the old site.
A new study of cannabis and brain damage is continuing to get a lot of publicity.
Study Strengthens Marijuana Brain Damage Case is the title of the accompanying headline.
Marijuana users who had smoked more than 5 joints a day (average of 11 joints a day) for more than 10 years (average use of 20 years) were tested.
They found that there was shrinkage in the amygdala and the hippocampus related to how much cannabis the person used.
The shrinkage was not large in either structure. The damage is described as “equivalent to mild traumatic brain injury or premature aging.” The article:
Doctors have known for years there is nothing “soft” about the drug cannabis. Professor Jon Currie is the director of addiction medicine at St Vincent’s Hospital in Melbourne.”This is a very exciting study because it proves for the first time what we have been really worried out. That brain problems are real and that people who smoke cannabis over a long term do get problems.” he said.
It’s also equivalent to drinking over 2 drinks per day. It’s equivalent to severe stress. It’s equivalent to having PTSD. It’s equivalent to all sorts of stuff.
This study was done by Nadia Solowij out of Australia. For whatever reason, every single study done by Solowij and colleagues seems to find pretty serious brain damage.
This study is pretty scary, but so far there have been four other studies of heavy cannabis users that did not find damage to the hippocampus or the amygdala.
An MRI study from 2005 of very heavy cannabis users who had used cannabis on average of 20,100 times found no damage to the hippocampus at all. A study of cannabis-using young adults from 2006 found no damage to the hippocampus, or to any other structure. And a third study also found no hippocampal damage .
The study of users from 2006 also found no damage to the amygdala. This study actually found that the hippocampus-amygdala was 5% larger in the cannabis users than in the non-users, but the difference was not thought to be significant.
So there you have it. There are some pretty scary new findings coming out about cannabis and damage to the limbic system, but things are still far from proven. The single study so hyped by the media nowadays has already been contradicted by four negative studies. You would think that the media might have noted that. You would think wrong.
The road forward? More studies, I guess. You could always try smoking less than five joints a day too, just to be on the safe side.