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 .
Cannabidiol (CBD) as an Adjunctive Therapy in Schizophrenia: A Multicenter Randomized Controlled Trial.
OBJECTIVE Research in both animals and humans indicates that cannabidiol ( CBD ) has antipsychotic properties . The authors assessed the safety and effectiveness of CBD in patients with schizophrenia . METHOD In an exploratory double-blind parallel-group trial , patients with schizophrenia were r and omized in a 1:1 ratio to receive CBD ( 1000 mg/day ; N=43 ) or placebo ( N=45 ) alongside their existing antipsychotic medication . Participants were assessed before and after treatment using the Positive and Negative Syndrome Scale ( PANSS ) , the Brief Assessment of Cognition in Schizophrenia ( BACS ) , the Global Assessment of Functioning scale ( GAF ) , and the improvement and severity scales of the Clinical Global Impressions Scale ( CGI-I and CGI-S ) . RESULTS After 6 weeks of treatment , compared with the placebo group , the CBD group had lower levels of positive psychotic symptoms ( PANSS : treatment difference=-1.4 , 95 % CI=-2.5 , -0.2 ) and were more likely to have been rated as improved ( CGI-I : treatment difference=-0.5 , 95 % CI=-0.8 , -0.1 ) and as not severely unwell ( CGI-S : treatment difference=-0.3 , 95 % CI=-0.5 , 0.0 ) by the treating clinician . Patients who received CBD also showed greater improvements that fell short of statistical significance in cognitive performance ( BACS : treatment difference=1.31 , 95 % CI=-0.10 , 2.72 ) and in overall functioning ( GAF : treatment difference=3.0 , 95 % CI=-0.4 , 6.4 ) . CBD was well tolerated , and rates of adverse events were similar between the CBD and placebo groups . CONCLUSIONS These findings suggest that CBD has beneficial effects  in patients with schizophrenia . As CBD 's effects do not appear to depend on dopamine receptor antagonism , this agent may represent a new class of treatment for the disorder
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 .