Subchronic treatment with St John's wort produces a positive shift in emotional processing in healthy volunteers

Background: The neurocognitive model of antidepressant treatment in depression states that antidepressants work by producing relatively immediate positive shifts in emotional processing, which translate into clinical improvement with time. St John's Wort has shown antidepressant potential in randomised controlled trials; however, its pharmacological actions are broad and it is unknown whether treatment also produces changes in emotional processing. Aims: We investigated whether short-term treatment with St John's wort has similar effects on emotional processing to those reported with other antidepressants such as selective serotonergic reuptake inhibitors. Methods: Forty-eight healthy participants were given St John's wort or placebo treatment for seven days. On day 7 they completed a battery of tasks to measure emotional processing and other elements of cognition. Results: St John's wort treatment produced similar changes to other antidepressants, for example reducing recognition of disgusted faces and attention to fearful faces, while increasing memory for positive words. We failed to find evidence for an effect of St John's wort on other aspects of cognition including working memory. Conclusions: These findings lend support to the theory that the production of early positive biases in emotional processing may be a common feature of all clinically effective antidepressants with diverse pharmacological mechanisms.