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 .
Delta-9-tetrahydrocannabinol (THC) serum concentrations and pharmacological effects in males after smoking a combination of tobacco and cannabis containing up to 69 mg THC
Rationale Δ9-Tetrahydrocannabinol ( THC ) is the main active constituent of cannabis . In recent years , the average THC content of some cannabis cigarettes has increased up to approximately 60 mg per cigarette ( 20 % THC cigarettes ) . The pharmacokinetics of THC after smoking cannabis cigarettes containing more than approximately 35 mg THC ( 3.55 % THC cigarettes ) is unknown . To be able to perform suitable exposure risk analysis , it is important to know if there is a linear relation at higher doses . Objectives The present study aim ed to characterise the pharmacokinetics of THC , the active metabolite 11-OH-THC and the inactive metabolite THC-COOH after smoking a combination of tobacco and cannabis containing high THC doses . Material s and methods This double-blind , placebo-controlled , four-way , cross-over study included 24 male non-daily cannabis users ( two to nine joints per month ) . Participants were r and omly assigned to smoke cannabis cigarettes containing 29.3 , 49.1 and 69.4 mg THC and a placebo . Serial serum sample s collected over a period of 0–8 h were analysed by liquid chromatography electrospray t and em mass spectrometry . Effects on heart rate , blood pressure and ‘ high ’ feeling were also measured . Results Mean maximal concentrations ( Cmax ) were 135.1 , 202.9 and 231.0 μg/L for THC and 9.2 , 16.4 and 15.8 μg/L for 11-OH-THC after smoking a 29.3- , 49.1- and 69.4-mg THC cigarette , respectively . A large inter-individual variability in Cmax was observed . Heart rate and ‘ high ’ feeling significantly increased with increasing THC dose . Conclusions This study demonstrates that the known linear association between THC dose and THC serum concentration also applies for high THC doses
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 .