LSD is a hallucinogenic drug synthesized in 1938. It causes visual hallucinations and alters perceptions of time and self. LSD is typically taken orally by absorbing blotter paper, liquid drops, or tablets that have been soaked in the drug. Effects begin within 90 minutes and can last up to 12 hours, causing dilated pupils, increased heart rate, and sensations that sounds and colors are merging. Around 200,000 people use LSD for the first time each year according to surveys, taking it for its psychedelic and recreational effects.