In 1967, LSD was briefly labeled a breaker of chromosomes
Two New York researchers have found the hallucinogenic drug will markedly increase the rate of abnormal change in chromosomes. [Scientists] tested LSD on cell cultures from the blood of two healthy individuals … [and] also found similar abnormal changes in the blood of a schizophrenic patient who had been treated with [LSD]. The cell cultures showed a two-fold increase in chromosomal breaks over the normal rate. — Science News, April 1, 1967.