Scientists analyzed 226 mushroom samples from about 30 psychotropic species to measure their psilocybin and related compound content. They found that the amounts of these compounds vary greatly, even within the same species, making it difficult to predict how strong a mushroom will be. The research shows that Psilocybe species generally contain the most psychoactive compounds, with some varieties containing over 15 times more psilocybin than others, highlighting safety concerns for users.