This is because there are a range of sub-types of the serotonin receptor and each sub-type has different effects when activated. For example, activating the 5-HT1A receptor can reduce anxiety (such as the drugs buspirone and trazodone), whereas activating 5-HT2A (such as psychedelics such as LSD do) can make you believe that there is a clown in your closet who wants you dead. Or alternatively, activating 5-HT1B (as the triptan class of drugs do) will treat migraines and cluster headaches. If you go messing around with serotonin, you’d better make sure you target the right receptor!
