Of these , the metabolite produces the greatest psychoactive effects .
Cannabidiol ( CBD ) is not psychoactive but plays a modulating role on cannabis psychoactive effects .
The proportion of 9-THC in plant material is higher ( up to 40 % ) than in other cannabinoids ( up to 9 % ) .
Conclusions Findings reveal that 9-THC contributes the most to cannabis psychoactivity .
Due to lower psychoactive potency and smaller proportions in plant material , other psychoactive cannabinoids have a weak influence on cannabis final effects .
Objective This systematic review aims to summarize current evidence on which naturally present cannabinoids contribute to  cannabis psychoactivity  , considering their reported concentrations and pharmacodynamics in humans .
Influence of cannabidiol on delta‐9‐tetrahydrocannabinol effects
Experiments investigating the possible interaction of tetrahydrocannabinol ( THC ) and cannabidiol ( CBD ) , two major components of marihuana , were conducted under controlled laboratory conditions in a double‐blind manner . In one study , 15 male volunteers were given placebo or 25 µg/kg of THC together with either placebo or 150 µg/kg of CBD by inhalation of the smoke of a single cigarette . All four treatments were assigned to each subject according to a series of Latin‐square design s. CBD significantly attenuated the subjective euphoria of THC . Psychomotor impairment due to THC was not significantly altered by the simultaneous administration of CBD , but a trend indicating a decrease in THC‐like effects was observed after the combination . When administered alone CBD was inactive for all the parameters measured . In a second study , 8 male subjects were given CBD ( 0 or 150 µg/kg ) by smoke inhalation 30 min before THC ( 0 or 25 µg/kg ) in a second cigarette . In contrast to the simultaneous administration of both drugs , CBD pretreatment did not alter the effects of THC on the parameters observed
Of these , the metabolite produces the greatest psychoactive effects .
Cannabidiol ( CBD ) is not psychoactive but plays a modulating role on cannabis psychoactive effects .
The proportion of 9-THC in plant material is higher ( up to 40 % ) than in other cannabinoids ( up to 9 % ) .
Conclusions Findings reveal that 9-THC contributes the most to cannabis psychoactivity .
Due to lower psychoactive potency and smaller proportions in plant material , other psychoactive cannabinoids have a weak influence on cannabis final effects .
Objective This systematic review aims to summarize current evidence on which naturally present cannabinoids contribute to  cannabis psychoactivity  , considering their reported concentrations and pharmacodynamics in humans .