Dissociable effects of acute antidepressant drug administration on subjective and emotional processing measures in healthy volunteers

Background We have previously shown that single doses of serotonin-selective and noradrenaline-selective antidepressant agents produce positive biases in measures of emotional processing in healthy volunteers. The aim of the present study was to confirm and extend this finding by studying the effects of a single dose of the selective serotonin and noradrenaline re-uptake inhibitor, duloxetine. Materials and methods Healthy volunteers were randomly allocated to double-blind administration of either duloxetine 60 mg orally or placebo. Participants then completed a battery of emotional-processing tasks measuring facial expression recognition, emotional memory and emotion-potentiated startle. Subjective state was measured using visual analogue scales throughout the test period. Results Duloxetine enhanced the recognition of both disgusted and happy facial expressions and increased memory intrusions for positive personality characteristics in the free recall test. There were no significant effects on startle responses. However, duloxetine was not well tolerated and was associated with a high level of negative subjective effects. Conclusions Despite the induction of negative subjective effects after duloxetine administration, some positive effects on emotional processing were seen in line with acute administration of serotonin-selective and noradrenaline-selective antidepressant agents. These results confirm the induction of fast changes in emotional processing in healthy volunteer groups and suggest a mechanism by which antidepressants may act in depression. Further studies are required to assess whether positive effects on emotional processing are more selective at a lower dose of duloxetine.