Induction of sister-chromatid exchanges in heroin-cannabis, heroin and cannabis addicts.

The aim of this study was to determine the frequency of sister-chromatid exchanges (SCEs) in heroin-cannabis, heroin and cannabis addicts. The group of 84 subjects consisted of 42 controls, 16 heroin-cannabis addicts, 12 heroin addicts and 14 cannabis addicts. The mean number of SCEs/cell was 12.95 in heroin-cannabis addicts, 12.05 in heroin addicts and 11.99 in cannabis addicts. These values are significantly (P less than 0.002) higher than the mean values found in controls. This increase in SCEs may be related to reduced DNA repair in chronic drug addicts, which would allow the fixation or retention of a greater fraction of the DNA lesions caused by normal environmental exposure.