This:
The authors interviewed 53 cluster headache patients who had used psilocybin or lysergic acid diethylamide (LSD) to treat their condition. Twenty-two of 26 psilocybin users reported that psilocybin aborted attacks; 25 of 48 psilocybin users and 7 of 8 LSD users reported cluster period termination; 18 of 19 psilocybin users and 4 of 5 LSD users reported remission period extension. Research on the effects of psilocybin and LSD on cluster headache may be warranted.
And
this:
In other words, should a pharmaceutical company or investment firm sink the hundreds of millions of dollars into research and the process to get, for example, non-psychedelic 2-Bromo-LSD approved by the FDA as a legitimate prescription drug, they would want a guarantee that they’d have a significant return on that money. To sell three pills a year to less than half a million people… you don’t have to be a mathematician to see that the financial return on that would not exist.
In other words, “psychedelics work so well, you take fewer doses,” says Halpern. “That’s a problem. They work too well to attract the research.”