It breaks down with exposure to ultraviolet light. In pure form, LSD is clear or white in color, has no smell, and is crystalline. The effects of LSD are thought to stem primarily from it being an agonist at the 5-HT 2A receptor, while how exactly LSD exerts its effects by agonism at this receptor are still not fully known, corresponding increased glutamatergic neurotransmission and reduced default mode network activity are thought to be key mechanisms of action. While overdose from LSD is unknown, LSD can cause injury and death as a result of accidents stemming from psychological impairment. In cases where this causes distress or impairment it is diagnosed as hallucinogen persisting perception disorder (HPPD). Common effects include visual snow and palinopsia. It is possible for LSD to induce either intermittent or chronic visual hallucinations, in spite of no further use. Adverse psychological reactions are possible, such as anxiety, paranoia, and delusions. Frequent use rapidly builds tolerance, requiring exponentially larger doses to feel an effect. LSD is considered to be non-addictive with low potential for abuse. It is most often sold on blotter paper and less commonly as tablets or in gelatin squares.
LSD is typically either swallowed or held under the tongue. The use of LSD among US adults increased 56.4% from 2015 to 2018. It was most popular in the 1960s to 1980s. As of 2017, about 10% of people in the United States have used LSD at some point in their lives, while 0.7% have used it in the last year. LSD is both the prototypical psychedelic and one of the 'classical' psychedelics, being the psychedelics with the greatest scientific and cultural significance. It is used mainly as a recreational drug or for spiritual reasons. LSD is also capable of causing mystical experiences and ego dissolution, albeit less frequently than compounds such as psilocybin. Effects typically begin within half an hour and can last for up to 20 hours. Dilated pupils, increased blood pressure, and increased body temperature are typical.
At sufficiently high dosages LSD manifests primarily visual, as well as auditory, hallucinations. Effects typically include intensified thoughts, emotions, and sensory perception. Lysergic acid diethylamide ( LSD), also known colloquially as acid, is a psychedelic drug.