Is LSD addictive?

LSD is not considered an addictive drug. Although addiction to hallucinogens is rare, poly-drug addicts (people who are addicted to several drugs) frequently abuse hallucinogens. However, LSD does produce tolerance, so some users who take the drug repeatedly must take higher doses to achieve the same effects. This is very dangerous given the unpredictability of the drug and dose. Cross-tolerance between LSD and other hallucinogens has been reported.