Animal and human studies indicate that cannabidiol (CBD), a major constituent of cannabis, has anxiolytic properties. However, no study to date has investigated the effects of this compound on human pathological anxiety and its underlying brain mechanisms. The aim of the present study was to investigate this in patients with generalized social anxiety disorder (SAD) using functional neuroimaging. Regional cerebral blood flow (rCBF) at rest was measured twice using (99m)Tc-ECD SPECT in 10 treatment-naïve patients with SAD. In the first session, subjects were given an oral dose of CBD (400 mg) or placebo, in a double-blind procedure. In the second session, the same procedure was performed using the drug that had not been administered in the previous session. Within-subject between-condition rCBF comparisons were performed using statistical parametric mapping. Relative to placebo, CBD was associated with significantly decreased subjective anxiety (p < 0.001), reduced ECD uptake in the left parahippocampal gyrus, hippocampus, and inferior temporal gyrus (p < 0.001, uncorrected), and increased ECD uptake in the right posterior cingulate gyrus (p < 0.001, uncorrected). These results suggest that CBD reduces anxiety in SAD and that this is related to its effects on activity in limbic and paralimbic brain areas.

No abstract

Electrodermal activity has been considered as a potential source to identify subgroups of schizophrenics. However, the neural mechanisms that are the base of the electrodermal responsiveness in schizophrenia are not well-known. The present study aimed to determine if schizophrenic patients with different skin conductance levels (SCL) show differences in grey matter (GM) volume estimated through VBM. Thirty-four schizophrenic patients paired with healthy volunteers, matched according to sex, age, handedness, socio-economic status and years of education, were selected. All patients were using anti-psychotics, and were included only when their score in the BPRS was lower then “present in mild degree” in all the scale items, except for negative symptoms. The electrodermal activity was measured during five minutes at rest and in comfortable conditions. Three groups were obtained, according to the electrodermal level: control, schizophrenic with normal SCL and schizophrenic with low SCL. MRI was performed with a Siemens Magneton 1.5T imaging system. The optimized VBM protocol was implemented within MATLAB 7.0 (Mathworks Inc.) through Statistical Parametric Mapping 2. Compared to controls, schizophrenic patients presented abnormalities in regional GM volume in superior and medial frontal lobes, paracentral lobule, cingulate, transverse temporal, insula, precuneus and occipital lobe. Regarding the schizophrenia groups, it was observed that the low SCL group presented smaller regional GM density in the right superior frontal lobe and in the right anterior cingulated. Accordingly, these results suggest that these brain areas may be involved in the modulation of SCL in schizophrenia and could be altered in a subgroup of patients.