Effects of delta-9-tetrahydrocannabinol on evaluation of emotional images

Abstract

There is growing evidence that drugs of abuse alter processing of emotional information in ways that could be attractive to users. Our recent report that Δ⁹-tetrahydrocannabinol (THC) diminishes amygdalar activation in response to threat-related faces suggests that THC may modify evaluation of emotionally-salient, particularly negative or threatening, stimuli. In this study, we examined the effects of acute THC on evaluation of emotional images. Healthy volunteers received two doses of THC (7.5 and 15 mg; p.o.) and placebo across separate sessions before performing tasks assessing facial emotion recognition and emotional responses to pictures of emotional scenes. THC significantly impaired recognition of facial fear and anger, but it only marginally impaired recognition of sadness and happiness. The drug did not consistently affect ratings of emotional scenes. THC's effects on emotional evaluation were not clearly related to its mood-altering effects. These results support our previous work, and show that THC reduces perception of facial threat. Nevertheless, THC does not appear to positively bias evaluation of emotional stimuli in general.

Figure 1

Mean (± SEM) percent correctly identified unambiguous (100% emotional intensity) angry, fearful, happy, and sad faces after placebo and Δ⁹-tetrahydrocannabinol (THC) (7.5 and 15 mg). THC significantly impaired recognition of unambiguous anger (15 mg) and fear (7.5 and 15 mg). *p<.025 compared with placebo, post hoc pairwise comparisons.

Figure 2

Mean (± SEM) percent correctly identified angry, fearful, happy, and sad faces of varying emotional intensity after placebo and Δ⁹-tetrahydrocannabinol (THC) (7.5 and 15 mg). Open circles represent placebo; gray triangles represent 7.5 mg THC; black squares represent 15 mg THC.