The chromosomes of lymphocytes were studied in 32 patients before and after they took lysergic acid diethylamide (LSD) as part of double-blind, controlled research of the effects of the drug in psychotherapy and in five black-market LSD users who volunteered to take pure LSD in a research setting. Statistical analysis revealed no significant difference between the before- and after-LSD chromosomal aberration rates. In addition, a post-LSD study of eight normal subjects who had received LSD in previous research experiments was also performed with the same cytogenetic methods. The results of these experiments consistently supported the conclusion that at this time there is no definite evidence that pure LSD damages chromosomes of human lymphocytes in vivo as studied from 72-hour cultures.
Tjio J, Pahnke WN, Kurland AA. LSD and ChromosomesA Controlled Experiment. JAMA. 1969;210(5):849-856. doi:10.1001/jama.1969.03160310037007