Kynurenine pathway in depression: A systematic review and meta-analysis

Kamiyu Ogyu, Kaoruhiko Kubo, Yoshihiro Noda, Yusuke Iwata, Sakiko Tsugawa, Yuki Omura, Masataka Wada, Ryosuke Tarumi, Eric Plitman, Sho Moriguchi, Takahiro Miyazaki, Hiroyuki Uchida, Ariel Graff-Guerrero, Masaru Mimura, Shinichiro Nakajima

Research output: Contribution to journalReview articlepeer-review

178 Citations (Scopus)


Abnormalities of the kynurenine (KYN) pathway may be implicated in the pathophysiology of depression. However, the relationships between depression and each metabolite of the KYN pathway remain uncertain. Therefore, we conducted a meta-analysis about the levels of the metabolites of KYN pathway between patients with depression and controls. Out of 899 initial records, we identified 22 articles to form the empirical basis. Seventeen, 10, and 18 studies examined levels of kynurenic acid (KYNA), quinolinic acid (QUIN), and KYN, respectively. KYNA and KYN levels were lower in patients with depression in comparison to controls, while QUIN levels did not differ between the two groups. Antidepressant-free patients showed decreased KYNA levels and increased QUIN levels compared with controls. Male ratios of the samples were negatively associated with study SMDs for KYNA. In conclusion, this meta-analysis revealed that patients with depression had decreased level of KYNA and KYN, whereas antidepressant-free patients showed increased level of QUIN. Nevertheless, given the heterogeneity among their sample characteristics, further research is clearly needed.

Original languageEnglish
Pages (from-to)16-25
Number of pages10
JournalNeuroscience and Biobehavioral Reviews
Publication statusPublished - 2018 Jul


  • Depression
  • Glutamate
  • Kynurenic acid
  • N-methyl-D-aspartate receptor
  • Neuroinflammation
  • Quinolinic acid

ASJC Scopus subject areas

  • Neuropsychology and Physiological Psychology
  • Cognitive Neuroscience
  • Behavioral Neuroscience


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