psychotropic (adj.)

word-forming element meaning "mind, mental; spirit, unconscious," from Greek combining form of psykhē "the soul, mind, spirit; life, one's life, the invisible animating principle or entity which occupies and directs the physical body; understanding, the mind (as the seat of thought), faculty of reason" (see psyche). It also was used to form compounds in Greek, such as psychapates "soul-beguiling" (with apate "deceit").

Proto-Indo-European root meaning "to turn."

It forms all or part of: apotropaic; atropine; Atropos; contrive; entropy; heliotrope; isotropic; psychotropic; retrieve; trope; -trope; trophy; tropic; tropical; tropism; troposphere; troubadour; zoetrope.

It is the hypothetical source of/evidence for its existence is provided by: Sanskrit trapate "is ashamed, confused," properly "turns away in shame;" Greek trepein "to turn," tropos "a turn, direction, course," trope "a turning;" Latin trepit "he turns."