Table 2.
Overview of studies investigating the effect of cannabidiol or cannabidiol in combination with THC on psychological functions in humans. Studies in which cannabis extracts have been used are not included.
| Reference | Subjects | Dosing THC/CBD | Results | Comments |
|---|---|---|---|---|
| Karniol et al. (64) | Healthy volunteers (n = 40) | 30 mg THC (oral); 15, 30 of 60 mg CBD (oral) or in combination with 30 mg THC (both oral) | Antagonizing (part of) the THC-induced effects | CBD decreased the anxiety component of THC effects; no effect of CBD alone |
| Hollister and Gillespie (65) | Healthy volunteers (n = 30) | 20 mg THC + 40 mg CBD (both oral) | CBD delays onset of the effect of THC and prolongs the effects of THC | |
| Dalton et al. (66) | Healthy volunteers (n = 15) | 25 μg/kg BW THC and 150 μg/kg BW CBD via smoking a joint | CBD reduces euphoric effect of THC | Only effective when CBD and THC are administered simultaneously |
| Hollister (67) | Healthy volunteers (n = ?) | CBD 5–30 mg i.v. | No effects | |
| Carlini and Cunha (68) | Healthy volunteers | Acute 600 mg CBD; 10 mg/kg/BW CBD 20 days | CBD does not have psychological or physical effects | Light drowsiness after CBD administration |
| Zuardi et al. (42) | Healthy volunteers (n = 8) | 0.5 mg/kg BW THC + 1 mg/kg BW CBD (both oral) | CBD antagonizes psychological effects of THC (anxiety) | CBD itself has no effect and does not antagonize the physical effects of THC (HR, BP) |
| Zuardi et al. (69) | Treatment resistant schizophrenic patients (n = 3) | CBD during 29 days upwards from 40 to 1280 mg/day (oral) | CBD does not antagonize symptoms | No side effects of CBD reported |
| Crippa et al. (70) | Healthy volunteers (n = 10) | CBD 400 mg oral | Anxiolytic effects; light mental sedation | SPECT results: effects in left amygdala-hippocampus complex radiating to hypothalamus |
| Leweke et al. (71) | Psychiatric patients (n = 43) | CBD oral 800 mg/day; during 4 weeks | CBD more effective as antipychotic than amsulpride | Less side effects of CBD than with amsulpride |
| Zuardi et al. (72) | PD patients with psychoses | CBD 150 mg/day; during 4 weeks | CBD possibly effective for treatment of PD patients suffering from psychoses | No significant side effects of CBD reported |
| Borgwardt et al. (73), Fusar-Poli et al. (74), Fusar-Poli et al. (75), Bhattacharyya et al. (76)a | Healthy volunteers (n = 15) | CBD oral 600 mg; 10 mg THC (not simultaneously); in comparison with placebo | No effect in contrast with THC; CBD activates other brain areas than THC no effects of CBD in verbal learning task and no induction of psychotic symptoms | No sedation and no inhibition of locomotion by CBD; THC induces psychotic symptoms, anxiety, and sedation |
| Zuardi et al. (77) | Patients with bipolar disorder (n = 2) | CBD oral 600 – 1200 mg/day during 25 days | CBD has no effect on symptoms | No side effects of CBD reported |
| Bhattacharyya et al. (43) | Healthy volunteers (n = 6) | CBD 5 mg i.v. immediately followed by 1.25 mg THC i.v. | CBD antagonizes THC-induced psychotic symptoms | CBD and THC have opposite effects on regional brain function |
| Bergamaschi et al. (78) | Healthy controls (n = 12) and patients with social phobia (n = 24) | CBD oral 600 mg | Reduction of anxiety scores in patients, no effect in controls | No physical effects or side effects of CBD reported |
| Crippa et al. (79) | Patients with social phobia (n = 10) | CBD oral 400 mg | No effect on psychological scores | No physical effects; SPECT: CBD exerts its effects via limbic and paralimbic areas |
| Nicholson et al. (80) | Healthy volunteers (n = 8) | CBD 5 mg + THC 5 mg; CBD 15 mg + THC 15 mg, via mouth spray | THC (15 mg) increases drowsiness, antagonized by CBD (15 mg) | |
| Hallak et al. (81) | Schizophrenic patients (n = 28) | CBD oral 300 and 600 mg acute | No positive effects in Stroop Color Word Test | No significant side effects of CBD reported |
| Hallak et al. (82) | Healthy volunteers (n = 10) | CBD oral 600 mg and ketamine i.v. | CBD increases activating effects of ketamine (BPRS); reduction of ketamine-induced depersonalization (CADSS) | No effect of CBD on HR and BP |
a This concerns experiments with one group of 15 subjects from which the results have been spread over four different publications; BP, blood pressure; BW, body weight; CADSS, Clinician Administered Dissociative States Scale; HR, heart rate; i.v., intravenously; PD, Parkinson disease.