Descriptive characteristics of probands by sex, challenge condition and COMT Val158Met genotype.

ITI startle = startle response during the intertrial interval in µV (ITI); Startle unpl = startle response after presentation of unpleasant IAPS pictures (in µV; T-transformed); Startle pl = startle response after presentation of pleasant IAPS pictures (in µV; T-transformed); Diffunpl-neutr = potentiation of startle magnitude by unpleasant IAPS pictures (in µV; T-transformed values: contrast unpleasant/neutral pictures); CTQ = Childhood Trauma Questionnaire (sum score).Note: Because of the large variance of caffeine saliva concentrations (difference of more than one and a half interquartile ranges from the respective median in the placebo or verum group) five subjects were excluded, leaving 85 subjects for further analyses when considering challenge condition. For the mean ITI startle response, one subject was excluded because of an extreme score (> three SD).