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 .
Cannabidiol inhibits THC-elicited paranoid symptoms and hippocampal-dependent memory impairment
Community-based studies suggest that cannabis products that are high in Δ9-tetrahydrocannabinol ( THC ) but low in cannabidiol ( CBD ) are particularly hazardous for mental health . Laboratory-based studies are ideal for clarifying this issue because THC and CBD can be administered in pure form , under controlled conditions . In a between-subjects design , we tested the hypothesis that pre-treatment with CBD inhibited THC-elicited psychosis and cognitive impairment . Healthy participants were r and omised to receive oral CBD 600 mg ( n=22 ) or placebo ( n=26 ) , 210 min ahead of intravenous ( IV ) THC ( 1.5 mg ) . Post-THC , there were lower PANSS positive scores in the CBD group , but this did not reach statistical significance . However , clinical ly significant positive psychotic symptoms ( defined a priori as increases ≥3 points ) were less likely in the CBD group compared with the placebo group , odds ratio (OR)=0.22 ( χ2=4.74 , p<0.05 ) . In agreement , post-THC paranoia , as rated with the State Social Paranoia Scale ( SSPS ) , was less in the CBD group compared with the placebo group ( t=2.28 , p<0.05 ) . Episodic memory , indexed by scores on the Hopkins Verbal Learning Task-revised ( HVLT-R ) , was poorer , relative to baseline , in the placebo pre-treated group ( -10.6±18.9 % ) compared with the CBD group ( -0.4%±9.7 % ) ( t=2.39 , p<0.05 ) . These findings support the idea that high-THC/low-CBD cannabis products are associated with increased risks for mental health
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 .