How do drugs affect the brain?

Psychedelics trigger psychedelic experiences

Question: How do drugs affect the brain?
Position1 of 3›: Hallucinogens alter perception and cause hallucinations
Argument‹2 of 2: Psychedelics trigger psychedelic experiences

Psychedelic experiences involve a feeling of altered or expanded consciousness, and may involve hallucinations.

The argument

Major psychedelic drugs include LSD, DMT, mescaline, and psilocybin. These drugs primarily act on serotonin receptors in the brain. Serotonin is an important neurotransmitter which affects many areas of brain function, including cognition, learning, and memory, but is most commonly associated with rewarding feelings of happiness and contentment. By acting on serotonin receptors and thus influencing the complex neurochemistry of serotonin, psychedelic drugs can trigger a myriad of changes to perception and consciousness, from trance-like states to flashbacks to psychotic episodes.

Premises

[P1]Major psychedelics like LSD, DMT, mescaline, and psilocybin act primarily on the brain's serotonin receptors. [P2] Serotonin governs cognition, learning, memory, and feelings of happiness, so disrupting it reshapes the brain's neurochemistry. [P3] This produces wide-ranging changes to perception and consciousness, from trance-like states to flashbacks and psychotic episodes. [C] Therefore, because psychedelics trigger these psychedelic experiences, hallucinogens alter perception and cause hallucinations.

Counter-arguments

A precision objection notes that classic psychedelics act specifically on the 5-HT2A serotonin receptor, not on serotonin receptors in general, so the broad-brush 'they act on serotonin' account obscures the actual mechanism. Serotonin's popular association with 'happiness and contentment' is itself an oversimplification, and disrupting one receptor subtype does not simply 'reshape' all of the brain's neurochemistry. Critics add that classic serotonergic psychedelics rarely produce true hallucinations — perceiving things that are wholly absent — but instead distort existing perception; this is why the label 'hallucinogen' is itself contested. Describing them as reliably causing 'hallucinations' and 'psychotic episodes' overstates the typical effect.

Rejecting the premises

[Rejecting P1] Psychedelics act specifically on the 5-HT2A serotonin receptor, not serotonin receptors generally; the broad account obscures the mechanism. [Rejecting P2] Serotonin's role in 'happiness and contentment' is itself an oversimplification, and disrupting one receptor subtype does not simply 'reshape' all the brain's neurochemistry. [Rejecting P3] Classic psychedelics rarely produce true hallucinations (perceiving things wholly absent); they more often distort existing perception, so 'cause hallucinations' and 'psychotic episodes' overstate the typical effect.