Editing Psychopharmacology (section)

==== Classical serotonergic psychedelics ====
[[Psychedelics]] cause perceptual and cognitive distortions without delirium. The state of intoxication is often called a "trip". Onset is the first stage after an individual ingests ([[LSD]], [[psilocybin]], [[ayahuasca]], and [[mescaline]]) or smokes ([[dimethyltryptamine]]) the substance. This stage may consist of visual effects, with an intensification of colors and the appearance of geometric patterns that can be seen with one's eyes closed. This is followed by a plateau phase, where the subjective sense of time begins to slow and the visual effects increase in intensity. The user may experience [[synesthesia]], a crossing-over of sensations (for example, one may "see" sounds and "hear" colors). These outward sensory effects have been referred to as the "mystical experience", and current research suggests that this state could be beneficial to the treatment of some mental illnesses, such as depression and possibly addiction.<ref>{{Cite book | vauthors = Pollan M |title=How to Change Your Mind: What the New Science of Psychedelics Teaches Us About Consciousness, Dying, Addiction, Depression, and Transcendence |publisher=Penguin Books |year=2019 |isbn=9780735224155}}</ref> In instances where some patients have seen a lack of improvement from the use of antidepressants, serotonergic hallucinogens have been observed to be rather effective in treatment.<ref name=":12">{{cite journal | vauthors = Dos Santos RG, Osório FL, Crippa JA, Hallak JE | title = Classical hallucinogens and neuroimaging: A systematic review of human studies: Hallucinogens and neuroimaging | journal = Neuroscience and Biobehavioral Reviews | volume = 71 | pages = 715–728 | date = December 2016 | pmid = 27810345 | doi = 10.1016/j.neubiorev.2016.10.026 | s2cid = 5261758 }}</ref> In addition to the sensory-perceptual effects, hallucinogenic substances may induce feelings of depersonalization, emotional shifts to a euphoric or anxious/fearful state, and a disruption of logical thought. Hallucinogens are classified chemically as either [[indolamines]] (specifically [[tryptamines]]), sharing a common structure with serotonin, or as [[phenethylamines]], which share a common structure with norepinephrine. Both classes of these drugs are [[agonist]]s at the 5-HT<sub>2</sub> receptors; this is thought to be the central component of their hallucinogenic properties. Activation of 5-HT<sub>2A</sub> may be particularly important for hallucinogenic activity. However, repeated exposure to hallucinogens leads to rapid tolerance, likely through down-regulation of these receptors in specific target cells.<ref name=Psychopharm /> Research suggests that hallucinogens affect many of these receptor sites around the brain and that through these interactions, hallucinogenic substances may be capable of inducing positive introspective experiences.<ref name=":12"/> The current research implies that many of the effects that can be observed occur in the occipital lobe and the frontomedial cortex; however, they also present many secondary global effects in the brain that have not yet been connected to the substance's biochemical mechanism of action.<ref name=":12" />