[2] Until recently, Deconica was generally considered to be synonymous with Psilocybe, and was originally named as a subgenus of Agaricus by Worthington George Smith in 1870.

However, the generally accepted lectotype (a specimen later selected when the original author of a taxon name did not designate a type) of the genus as a whole was Psilocybe montana, a non-hallucinogenic species; if those forms of the species in the study were to be segregated, it would leave the hallucinogenic clade without a valid name.

[8] Recently, it has been reported that the non-bluing Psilocybe fuscofulva does not produce hallucinogenic compounds.

Deconica had previously been recognized as a separate genus by several authors, including Rolf Singer in 1951,[10] Dennis and Orton in 1960,[11] and Horak in 1979.

[12] Many species in Deconica were transferred there by mycologist Machiel Noordeloos in a 2009 publication.