INTERPRETATION A single THC administration induces psychotic , negative , and other psychiatric symptoms with large effect sizes .
There is no consistent evidence that CBD induces symptoms or moderates the effects of THC .
BACKGROUND Approximately 188 million people use cannabis yearly worldwide , and it has recently been legalised in 11 US states , Canada , and Uruguay for recreational use .
The potential for increased cannabis use highlights the need to better underst and its risks , including the acute induction of psychotic and other psychiatric symptoms .
We aim ed to investigate the effect of the cannabis constituent Δ9-tetrahydrocannabinol ( THC ) alone and in combination with cannabidiol ( CBD ) compared with placebo on psychiatric symptoms in healthy people .
Individual and combined effects of acute delta-9-tetrahydrocannabinol and cannabidiol on psychotomimetic symptoms and memory function
The main active ingredient in cannabis , delta-9-tetrahydrocannabinol ( THC ) , can acutely induce psychotic symptoms and impair episodic and working memory . Another major constituent , cannabidiol ( CBD ) , may attenuate these effects . This study aim ed to determine the effects of THC and CBD , both alone and in combination on psychotic symptoms and memory function . A r and omised , double-blind crossover design compared the effects of ( i ) placebo , ( ii ) THC 8 mg , ( iii ) CBD 16 mg and ( iv ) THC 8 mg + CBD 16 mg administered by inhalation through a vaporiser . Using an experimental medicine approach to predict treatment sensitivity , we selected 48 cannabis users from the community on the basis of ( 1 ) schizotypal personality question naire scores ( low , high ) and ( 2 ) frequency of cannabis use ( light , heavy ) . The Brief Psychiatric Rating Scale ( BPRS ) , Psychotomimetic States Inventory ( PSI ) , immediate and delayed prose recall ( episodic memory ) , 1- and 2-back ( working memory ) were assessed on each day . Results indicated that THC increased overall scores on the PSI , negative symptoms on BPRS , and robustly impaired episodic and working memory . Co-administration of CBD did not attenuate these effects . CBD alone reduced PSI scores in light users only . At a ratio of 2:1 , CBD does not attenuate the acute psychotic and memory impairing effects of vaporised THC . Frequent cannabis users may show a blunted anti- psychotic response to CBD , which is of concern due to the high rates of cannabis use disorders in patients with schizophrenia
INTERPRETATION A single THC administration induces psychotic , negative , and other psychiatric symptoms with large effect sizes .
There is no consistent evidence that CBD induces symptoms or moderates the effects of THC .
BACKGROUND Approximately 188 million people use cannabis yearly worldwide , and it has recently been legalised in 11 US states , Canada , and Uruguay for recreational use .
The potential for increased cannabis use highlights the need to better underst and its risks , including the acute induction of psychotic and other psychiatric symptoms .
We aim ed to investigate the effect of the cannabis constituent Δ9-tetrahydrocannabinol ( THC ) alone and in combination with cannabidiol ( CBD ) compared with placebo on psychiatric symptoms in healthy people .