Cluster headaches, anxiety, and depression can be debilitating for people living with these conditions.  Psychedelic drugs have been shown in clinical trials to be effective as a treatment for these conditions, but not for everyone. Researchers told an article published in the journal ACS Chemical Neuroscience that one reason may be common genetic variations in a single serotonin receptor. They found that seven variants uniquely and differentially affect the receptor's response to four psychedelic drugs -- psilocin, LSD, 5-methoxy-dimethyltryptamine and mescaline. Recently there has been renewed interest in psychedelic compounds that stimulate serotonin receptors in the brain, thanks to several promising results from clinical trials. These receptors bind serotonin and other similar amino-containing molecules that help regulate people's mood, perception, cognition and emotions, as well as their appetite. In particular, the serotonin receptor known as 5-HT2A is responsible for mediating the effects of psychedelic drugs. However, there are several natural, random genetic variations known as single-nucleotide polymorphisms that can affect the structure and function of the 5-HT2A receptor. Therefore, the scientists wanted to study how variations in the serotonin 5-HT2A receptor affect the activity of four psychedelic drugs. Based on their findings, the researchers expect that patients with different genetic variations will respond differently to treatment with psychotropic drugs. They suggest that physicians consider a patient's serotonin receptor genetics to determine which psychedelic compound may be the most effective treatment.