Psilocybin causes delayed-onset headaches in healthy people
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3345296

Psilocybin stops cluster headache in patients suffering from frequent cluster headache attacks
https://www.ncbi.nlm.nih.gov/m/pubmed/16801660/

What's going on here? The speculation is that it's due to psilocybin's similarity to tryptophan, which is known to modulate headaches.