The ability for a substance to be psychoactive(noun)
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Use "psychoactivity" in a sentence
"At the point where people realised that psychoactivity was making as many brain-fried fuck-ups as boddhisatvas, the dream started to crumble from within."
"The paper provides no URL to the i-doser sites allegedly peddling these aural intoxicants, so there's no way for the reader to investigate the psychoactivity of the beats themselves."
"However, within a few hours of smoking marijuana, the amount of THC in the brain falls below the concentration required for detectable psychoactivity."