The connoisseurs hold out for (−)-trans-Δ9-tetrahydrocannabinol.

THC, or Δ⁹-tetrahydrocannabinol, is the principal psychoactive compound found in cannabis. Its molecular formula is C₂₁H₃₀O₂, and its structure allows it to interact with cannabinoid receptors in the human nervous system. THC acts primarily as a partial agonist of CB₁ receptors in the brain, altering neurotransmitter release and producing changes in perception, mood, memory, coordination, and appetite. It can also activate CB₂ receptors, which are more closely associated with immune tissues. Its effects vary with dose, route of administration, and individual physiology. THC is used in research, pharmaceuticals, and recreational products.