Table 2.
Group differences in tryptophan and its catabolites between healthy controls (HC), patients with schizophrenia (SZ) or major depressive disorder (MDD).
| HC (n = 19) | SZ (n = 45) | MDD (n = 43) | Statistics | ||||||
|---|---|---|---|---|---|---|---|---|---|
| Test statistics (uncorrected) | Post-hoc (uncorrected) | Test statistics (corrected6) | Post-hoc (corrected6) | ||||||
| Tryptophan3 (nM) | 58,539.56 ± 11,511.48 | 57,624.27 ± 9738.86 | 56,094.68 ± 9774.15 | F(2,97) = 0.44 | p = 0.6481 | F(2, 97) = 0.313 | 6p = 0.732 | ||
| Kynurenine (nM) | 2258.92 ± 736.61 | 2089.81 ± 450.33 | 2015.96 ± 401.99 | F(2,97) = 1.59 | p = 0.2091 | F(2, 97) = 3.24 | p = 0.0436 |
p = 0.067a p = 0.016b p = 0.622c |
|
| Tryptophan / Kynurenine | 28.16 ± 8.57 | 28.89 ± 8.10 | 28.57 ± 6.00 | F(2,97) = 0.068 | p = 0.9341 | F(2, 97) = 1.13 | p = 0.3276 | ||
| Kynurenic Acid4 (nM) | 55.48 ± 24.56 | 50.55 ± 20.93 | 46.06 ± 28.87 | KWS = 7.53 | p = 0.0232 |
p > 0.999a p = 0.046b p = 0.098c |
F(2, 97) = 1.01 | p = 0.3686 | |
| 3-Hydroxy Kynurenine (nM) | 37.09 ± 13.58 | 31.99 ± 9.25 | 30.24 ± 7.17 | F(2,97) = 3.50 | p = 0.0341 |
p = 0.122a p = 0.026b p = 0.660c |
F(2, 97) = 3.11 | p = 0.0496 |
p = 0.068a p = 0.019b p = 0.661c |
| Kynurenine / 3-Hydroxy Kynurenine | 62.54 ± 11.46 | 68.43 ± 15.91 | 68.99 ± 15.84 | F(2,97) = 1.30 | 1p = 0.277 | F(2, 97) = 0.12 | p = 0.8896 | ||
| Kynurenic Acid / 3-Hydroxy Kynurenine4,5 | 1.48 ± 0.32 | 1.63 ± 0.58 | 1.50 ± 0.75 | F(2,97) = 0.38 | p = 0.6841 | F(2, 97) = 0.074 | p = 0.9296 | ||
| Quinolinic Acid (nM) 4,5 | 378.93 ± 478.46 | 341.38 ± 177.23 | 270.98 ± 105.48 | KWS = 2.47 | p = 0.2902 | F(2, 97) = 0.31 | p = 0.7326 | ||
| Kynurenic Acid / Quinolinic Acid4,5 | 0.23 ± 0.11 | 0.18 ± 0.10 | 0.18 ± 0.10 | KWS = 4.63 | p = 0.102 | F(2, 97) = 0.1 | p = 0.9086 | ||
Statistics: 1One-way analysis of variance, 2Kruskal-Wallis test, Post-hoc (Tukey’s test for post-hoc comparisons of ANOVAs and Dunn’s test for post-hoc comparison of Kruskal–Wallis tests): aHC vs. SZ, bHC vs. MDD, cSZ vs. MDD. 3log10-transformation achieved normal distribution in HC, 4log10-transformation achieved normal distribution in patients with SZ. 5log10-transformation achieved normal distribution in patients with MDD. 6General linear model with age, sex, BMI, smoking and medication (chlorpromazine equivalents, imipramine equivalents, lorazepam medication) as covariates (post-hoc comparison: least significant difference). Data is presented as mean ± standard deviation. The level of significance was set at p < 0.05 (significant p-values are indicated in bold).