Mental stress and gastric acid secretion. Do personality traits influence the response?

In 14 healthy male volunteers, we studied the influence of acute mental (= psychological) stress induced by performing mental arithmetic and solving anagrams against a financial reward on endogenously stimulated gastric acid output. Personality factors were determined by the Personality Research Form. Acute mental stress significantly (P less than 0.05) increased systolic blood pressure (+8.9 +/- 2.0 mm Hg +/- SEM) and heart rate (+5.3 +/- 1.6 beats/min). The mean gastric acid output during the mental stress period (17.9 +/- 2.7 mmol/32 min) did not significantly differ from pre- (16.9 +/- 2.3 mmol/32 min) and poststress (18.1 +/- 2.2 mmol/32 min) values. However, detailed analysis revealed that mental stress induced contrary changes of gastric acid output in different subjects. About half the individuals reacted with a decrease (up to 60%) and the other half with an increase (up to 60%) in acid output. In some individuals the changes of gastric acid output were very small. By multiple correlations, impulsivity was identified as the personality trait with the highest correlation coefficient (r = 0.82) with changes of gastric acid output during the acute mental stress period. During the mental stress period, gastric acid output increased in subjects with high scores on the impulsivity scale, but significantly decreased in those with low scores. We conclude that (1) there is a great individual variability in gastric acid response to acute mental stress, and (2) this variability may be partly attributed to differences in personality traits.