The authors measured platelet MAO activity with phenylethylamine and
tryptamine substrates in a group of 20 subjects with chronic anxiety before
and after they underwent relaxation training. Levels of anxiety were
quantified using a self-rating scale. Posttreatment values for anxiety and
enzyme activity were significantly lower than pretreatment values. Anxiety
and enzyme activity levels were not significantly correlated at any stage
of the study.