Before we get into the details, and explore why I never get invited to participate in trials like this, let me set the stage by noting that LSD is an agonist at many serotonin and dopaminergic receptors in the brain. And LSD has multiple effects. There’s the sensory effects – synesthesia, hallucination. There’s the euphoria. But LSD, and several other drugs including marijuana, also stimulate brain centers that attach meaning to external stimuli. Remember when you were smoking pot in college and had that amazing conversation that was so meaningful? Yeah, it probably wasn’t.

But I’ve always thought this is what makes some of these drugs attractive – they make our mundane existence seem more important.

The hypothesis is that all of these diverse effects would be mediated by diverse receptors in the brain. But this study found just the opposite. Nearly all of LSDs effects operated through one receptor.

Researchers took 21 volunteers in a double-blind, randomized, cross-over design, and exposed each of them to 3 conditions. Placebo, LSD – 100 micrograms which is a decent, but not crazy dose, or LSD plus an antagonist to the serotonin 2a receptor called ketanserin.

If you look at figure 1, you can see that the serotonin 2A blocker basically negated all the effects of LSD: