Klaassen T, Klumperbeek J, Deutz N E, van Praag H M, Griez E
Department of Psychiatry and Neuropsychology, Maastricht University, The Netherlands.
Psychiatry Res. 1998 Feb 27;77(3):167-74. doi: 10.1016/s0165-1781(98)00004-3.
Results of several studies suggest that anxiety is under serotonergic control. We studied the influence of tryptophan depletion on generalized anxiety and on the response to a 35% carbon dioxide (CO2) challenge. Fifteen healthy male volunteers received both a mixture of amino acids without tryptophan and a placebo mixture under double-blind conditions. The tryptophan-free mixture led to an 80% decrease in blood tryptophan levels compared to the placebo. There was a significant increase in anxiety on the Spielberger Anxiety Inventory and a trend towards more tension on the Profile of Mood States-'tension' items, both of which were interpreted as increased nervousness. Furthermore, a significant increase in neurovegetative panic symptoms occurred after the CO2 challenge. We conclude that the serotonergic system is causally involved in anxiety-related mechanisms and that it may be worth pursuing the role of tryptophan depletion on CO2-induced panic in patients with anxiety disorders.
