Scott Alexander explores Hallucinogen Persisting Perception Disorder (HPPD) and other conditions where drugs cause permanent effects, discussing potential mechanisms and their implications. Longer summary

Scott Alexander discusses Hallucinogen Persisting Perception Disorder (HPPD), a condition where some people experience permanent hallucinatory effects after using psychedelic drugs, particularly LSD. He explores the prevalence, potential mechanisms, and implications of this disorder. The post compares HPPD to other conditions with persistent effects like tardive dyskinesia, and examines various theories about how drugs could cause permanent changes in the brain. Scott considers two main hypotheses: the killing-off of specific neurons, and the idea of the brain as a chaotic system settling into new attractor states. He expresses a preference for the neuron death theory as it seems more understandable and less scary, but acknowledges the complexity and uncertainty surrounding these issues. Shorter summary