Studies in Humans
In human studies, CBD administration did not induce side effects across a wide range of dosages, including acute and chronic dose regimens, and tolerance to CBD did not develop.
Acute Studies In the 1970s, human studies showed that oral CBD intake from 15 to 160mg [61-63], inhalation of 0.15mg/kg bw [64]or intravenous injection from 5 to 30mg [4][61] were not followed by ill effects.
CBD does not interfere with several psychomotor and psychological functions in humans. CBD does not affect heart rate, blood pressure, or performance in the verbal paired-associate learning test as measured by recall score at doses up to 600mg [5][62][65][74].
Subsequent studies concerning the antipsychotic effects of CBD have not reported any side effects after CBD intake[75-77].
Chronic Studies Chronic oral administration of 10mg CBD daily for 21 days did not induce any changes in neurological (including electroencephalogram (EEG)), clinical (including electrocardiogram (EKG)), psychiatric, blood or urine examinations [78].
Likewise, oral CBD administration in healthy participants (3mg/kg bw daily for 30 days) and in epileptic patients (200-300mg daily for 135 days) was well tolerated and no signs of toxicity or serious side effects were detected on neurological and physical examinations, blood and urine analysis, or EKG and EEG, which were performed at weekly intervals [10].
CBD was evaluated for symptomatic efficacy and safety in 15 neuroleptic-free patients with Huntington's Disease.Effects after oral CBD (10mg/kg bw /day for 6 weeks) or placebo (sesame oil for 6 weeks) intake were evaluated weekly under a double-blind, randomized crossover design.
CBD showed no significant or clinical differences compared to placebo in the Cannabis side effect inventory, clinical lab tests or other safety outcome variables. Also, weekly plasma levels of CBD (mean range 5.9 to 11.2 ng/ml), assayed by GC/MS, did not differ significantly over the 6 weeks of CBD administration [79].