Plasma kynurenine and related measures in tic disorder patients

  • Pieter J. Hoekstra
  • George M. Anderson
  • Pieter W. Troost
  • Cees G. M. Kallenberg
  • Ruud B. Minderaa

DOI: 10.1007/s00787-007-1009-1

Cite this article as:
Hoekstra, P.J., Anderson, G.M., Troost, P.W. et al. Eur Child Adolesc Psychiatry (2007) 16(Suppl 1): 71. doi:10.1007/s00787-007-1009-1



Increased plasma kynurenine has been reported in tic disorder patients, and this observation has been suggested to be indicative of immune dysregulation. In the present study, we examined plasma levels of kynurenine and related molecules in a group of tic disorder patients.


Plasma concentrations of tryptophan, kynurenine, cortisol, and neopterin were determined in Dutch tic disorder patients (N = 59), and healthy volunteers (N = 32). Group means were compared and age-controlled intra-individual correlations between tic severity and plasma levels of these molecules were examined.


No significant differences were found between patient and control groups in plasma levels of tryptophan, kynurenine, and cortisol concentrations, nor in the kynurenine/tryptophan ratio. However, neopterin was significantly (= 0.035) higher in patients (mean = 5.13 nmol/l) than in controls (mean = 3.30 nmol/l). Plasma levels of these molecules did not correlate with tic severity, with the exception of tryptophan (r = −0.289, = 0.049). In patients, plasma neopterin correlated with kynurenine (r = 0.438, = 0.002); in healthy subjects, tryptophan correlated with kynurenine (r = 0.670, < 0.001).


While the observed elevation in plasma neopterin is consistent with immune activation in a subset of tic disorder patients, metabolism of tryptophan through the kynurenine pathway appears to be unaltered in tic disorder patients.


tic disorders kynurenine tryptophan neopterin indoleamine 2,3-dioxygenase cortisol 



indoleamine 2,3-dioxygenase

K/T ratio

kynurenine to tryptophan ratio


tryptophan 2,3-dioxygenase

Copyright information

© Steinkopff Verlag Darmstadt 2007

Authors and Affiliations

  • Pieter J. Hoekstra
    • 1
  • George M. Anderson
    • 2
  • Pieter W. Troost
    • 1
  • Cees G. M. Kallenberg
    • 3
  • Ruud B. Minderaa
    • 1
  1. 1.Department of PsychiatryUniversity Medical Center Groningen, University of GroningenGroningenThe Netherlands
  2. 2.Yale Child Study CenterNew HavenUSA
  3. 3.Department of Clinical ImmunologyUniversity Medical Center Groningen, University of GroningenGroningenThe Netherlands

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