Investigators from the United Kingdom and the Netherlands performed functional magnetic resonance imaging (fMRI) on 11 healthy male subjects. Following the administration of THC or placebo, researchers assessed subjects’ brain activity during their exposure to stimuli with a negative (‘fearful faces’) content or a positive content (‘happy faces’). They hypothesized that THC administration would reduce subjects’ negative bias in emotional processing and shift it towards a positive bias. A bias toward negative stimuli has been linked to diagnoses of certain mental illnesses such as depression.
As anticipated, authors reported a reduction brain activity after THC administration when subjects’ processed stimuli with a negative emotional content. Conversely, researchers reported increased brain activity following THC administration when subjects’ processed stimuli with a positive emotional content.
They concluded: “These results indicate that THC administration reduces the negative bias in emotional processing. This adds human evidence to support the hypothesis that the endocannabinoid system is involved in modulation of emotional processing. Our findings also suggest a possible role for the endocannabinoid system in abnormal emotional processing, and may thus be relevant for psychiatric disorders such as major depression.”
An abstract of the study, “The endocannabinoid system and emotional processing: A pharmacological fMRI study with ?9-tetrahydrocannabinol,” appears online here.