Hallucinogens
Hallucinogenic drugs distort one's perspective of objective reality. If taken in high quantities, delusions and hallucinations are characteristic of this class of drugs.
It is also common for a user to experience unpleasant psychological reactions, including panic, anxiety, loss of control, and disorienting flashbacks.
Hallucinogens commonly seen by the laboratory include: lysergic acid diethylamine (LSD), psilocybin mushrooms, phencyclidine (PCP), and mescaline (peyote cactus).