Tryptophan & Emotional Processing (2006)
This study assessed tryptophan & emotional processing. It explored whether tryptophan (TRP) induces cognitive changes opposite to the negative biases found in depression and characteristic of those induced by serotonergic antidepressants in healthy volunteers. Thirty eight healthy volunteers were randomised to receive 14 days double-blind intervention with TRP (1g for 3x a day) or placebo. On the final day, emotional processing was assessed using four tasks: facial expression recognition, emotion-potentiated startle, attentional probe and emotional categorisation and memory. The results showed that TRP increased the recognition of happy facial expressions and decreased the recognition of disgusted facial expressions in female, but not male, volunteers. TRP also reduced attentional vigilance towards negative words and decreased baseline startle responsivity in the females. It concludes that these findings provide evidence that TRP supplementation in women induces a positive bias in the processing of emotional material that is reminiscent of the actions of serotonergic antidepressants. This highlights a key role for serotonin in emotional processing and lends support to the use of TRP as a nutritional supplement in people with mild depression or for prevention in those at risk.
Murphy SE et al. ‘Tryptophan supplementation induces a positive bias in the processing of emotional material in healthy female volunteers’. Psychopharmacology (Berl). 2006 Jul;187(1):121-30. Epub 2006 May 4
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