Rationale: Loosening legislation and changing perspectives have led to an increase in the use of CBD products despite some indications that CBD may not be completely safe. 

Method: About 200 healthy nonsmoking adults participated in this 28-day, double-blind study. 151 participants received an oral solution of CBD twice a day, totalling 5 mg/kg, within the range of reported consumer use, about 300mg a day. 50 participants received an inactive oral solution, or placebo. Although concentrations in unregulated over-the-counter CBD products can vary this study was conducted with the only FDA approved CBD. 

Results: 5.6% of healthy adults administered CBD had elevated liver enzymes, while none of the participants receiving placebo showed liver enzyme level elevations. Seven participants from the CBD group met criteria for drug-induced liver injury. In addition, 9% of the CBD-treated group had elevated white blood cells, or eosinophilia.

Meaning: CBD may not be as safe as people believe. Even one month of use produced liver damage in some subjects. Although liver function returned to normal 1 to 2 weeks following discontinuation, these findings suggest caution when using, or considering use of CBD.