How about weed for Alzheimer's disease?

A few months ago during Q&A after a talk, someone asked me whether marijuana might be good for treating Alzheimer's disease.  The question caught me cold, and I didn't go research what the person might have been talking about.  The person asking the question seemed to be disappointed that I didn't have much of an answer for her.  I had seen and heard nothing about this, and I probably didn't take the question seriously.

Then, two weeks ago, I got an email from my sister (the one who asked if I was following the research on intermittent fasting) asking me if I was following the research on THC as a treatment for Alzheimer's disease.  Well ... no, I wasn't.  So she sent me a link to this article in Discover magazine (and some others).  It was very interesting.

I think everyone reading this knows that THC is the active ingredient in marijuana.

The first thing to note is that all of the research discussed in the article was done with mice.  No people.  So how transferable are the results?  I suppose we'll need to wait for actual human tests to know for sure.  But here's the upshot of what happened with the mice.

It's well established that long-term exposure to THC has a bad effect on the parts of the brain involved with memory.  And so it was with the mice... at least the young ones.  But the older mice?  Exposure to THC seemed to actually improve the cognition of certain older mice. 

The key to understanding what's going on are the "CB1" receptors on brain cells.  According to the article, these receptors are activated by THC molecules, and that leads to humans feeling stoned.  But there are CB1 receptors distributed throughout the brain, and their activation in some locations apparently leads to other results.

Some German research discussed in the article used mice whose genome -- their DNA -- had been edited to omit the CB1 receptors.  These are called "knockout mice," since some of their genes have been "knocked out" of their DNA.   The mice would be born without the CB1 receptors.  These mice, it turns out, were "dumber" than mice with normal receptors.  They went into cognitive decline when they were about 35 in mouse years.

But a mystery emerged.  Scientists in Brussels doing similar experiments found that their knockout mice were smarter than normal.  What was the difference?  The mice tested in Brussels were tested when they were teenagers -- in mouse years.  So elimination of the CB1 receptors only negatively affected the cognition of the older mice.  Therefore, it may be that stimulating the CB1 receptors with THC in older mice might impede cognitive decline.  This is a great topic for future research.

Does this have implications for Alzheimer's disease?  Or, if it turns out to be helpful for humans, would any benefit be restricted to memory loss from normal aging?  More research is required.  Currently, Europe seems to be where the most interest lies, but the article cites some regulatory hurdles there for work with marijuana.

American drug companies seem to be disinterested, perhaps because this may all flow from a drug that anyone can grow themselves.  Not only that, drug trials have had trouble recruiting test subjects when they fear they could end up with the placebo.  And my thought -- wouldn't any test subject perceive pretty quickly that they were or were not on the placebo?