A hallucination is a sensory experience that appears real but is generated by the mind, rather than by external stimuli. These perceptions can involve any of the five senses: sight, sound, smell, touch, or taste. While hallucinations can be a symptom of various conditions, certain substances are known to induce these altered states of perception, making individuals see, hear, or feel things that are not present in reality.
Categories of Hallucinogenic Drugs
Hallucinogenic drugs are broadly categorized based on their primary effects and chemical structures. The two main classifications are classic hallucinogens, often referred to as psychedelics, and dissociative drugs. A third category includes deliriants.
Classic hallucinogens primarily alter thoughts, mood, and perception, often leading to a perceived “expansion of consciousness.” Users typically remain aware that their perceptions are not real, even as they experience vivid visual and auditory changes.
Dissociative drugs, in contrast, induce a feeling of detachment or separation from one’s body or environment. While they can also cause hallucinations, these are often accompanied by a sense of being disconnected from reality. Deliriants primarily cause a state of delirium, characterized by confusion, disorientation, and more realistic hallucinations where the individual may not distinguish between what is real and unreal.
Common Hallucinogenic Substances and Their Effects
Classic hallucinogens include several well-known substances, each producing distinct experiences. Lysergic acid diethylamide (LSD), a potent synthetic compound, can cause a kaleidoscope of visual patterns and profound changes in perception, sometimes leading to a blending of senses, such as “smelling sounds” or “hearing colors.” The effects of LSD can last for an extended period, typically between nine and twelve hours.
Psilocybin, found in certain mushroom species, induces visual and auditory distortions and can promote feelings of insightfulness or connection. Dimethyltryptamine (DMT), a naturally occurring psychedelic, produces intense but short-lived hallucinogenic effects, including vivid visions and sensory crossovers. Mescaline, derived from the peyote cactus, can lead to vivid mental images, an altered perception of space and time, and a distorted sense of one’s body, with effects lasting around twelve hours.
Dissociative hallucinogens include substances like phencyclidine (PCP) and ketamine. PCP can cause users to feel removed from their body and environment, leading to a trance-like state, and may also induce vivid visual and auditory hallucinations. Ketamine, used medically as an anesthetic, can produce an out-of-body sensation characterized by a near-complete sensory detachment. Dextromethorphan (DXM), a common cough suppressant, can also induce dissociative and hallucinogenic effects at high doses, leading to distorted visual perceptions.
Deliriants, such as atropine and scopolamine, found in plants like Datura and deadly nightshade, cause a state of delirium rather than typical psychedelic hallucinations. Users may experience realistic hallucinations and have conversations with imaginary people, with little to no recollection of the experience afterward. Diphenhydramine, an over-the-counter antihistamine, can also act as a deliriant in higher than recommended doses.
How Hallucinogens Alter Perception
Hallucinogenic drugs alter perception by interfering with the brain’s normal communication pathways, particularly by affecting certain neurotransmitter systems. Classic hallucinogens, including LSD and psilocybin, primarily interact with serotonin 2A (5-HT2A) receptors in the brain. These drugs mimic serotonin, binding to and activating these receptors, which influence sensory perception, mood, and cognition.
Activation of 5-HT2A receptors is a primary mechanism in producing the hallucinatory state. This interaction modulates the balance of excitatory and inhibitory signals in brain circuits, leading to altered perception and consciousness.
Dissociative drugs, such as PCP and ketamine, work through a different mechanism by disrupting the actions of glutamate, a major excitatory neurotransmitter, at N-methyl-D-aspartate (NMDA) receptors. Glutamate plays a role in learning, memory, emotion, and pain perception. By blocking these NMDA receptors, dissociatives interfere with the normal signaling of glutamate, leading to sensory deprivation, hallucinations, and a feeling of detachment from reality.
Potential Risks and Adverse Effects
The use of hallucinogenic drugs carries various immediate and short-term risks, which can range from mild discomfort to severe psychological distress. One common adverse reaction is a “bad trip,” characterized by intense anxiety, panic, paranoia, and nightmarish hallucinations.
Beyond psychological distress, hallucinogens can exacerbate underlying mental health conditions, potentially triggering or worsening psychosis in vulnerable individuals. This includes aggressive behavior or psychotic symptoms, as seen with high doses of PCP. Users may experience disorganized thinking, delusions, and persistent visual disturbances even after the drug’s effects have worn off.
Physical risks can include increased heart rate, elevated blood pressure, nausea, vomiting, and excessive sweating. Disorientation and impaired judgment caused by these substances can also lead to accidents or injuries. While fatal overdoses from classic hallucinogens are rare, certain dissociative drugs like PCP and DXM can cause seizures, coma, or even death at high doses.