Rates of depression continue to rise every year, with over 7% of the adult US population experiencing at least one major depressive episode in 2017.
Numerous studies point to the hypothesis that inflammation could be the root cause of clinical depression. The kynurenine (KYN) pathway is one pathway for metabolising tryptophan, which is a precursor for serotonin, the ‘happiness hormone’. Low levels of tryptophan could explain depression and sleep disorders.
A new study published in Scientific Reports analysed blood serum levels of tryptophan metabolites from 61 participants considered at-risk of depression. A higher serum level of anthranilic acid and women who were more likely to develop depression had lower levels of tryptophan.
To predict the progression of depression, data from 33 individuals whose clinical depression scores indicated a clear progression towards the condition were analysed. A clear correlation over time between increasingly high levels of anthranilic acid and increasingly severe depression were found.
Tryptophan metabolite levels were measured in individuals with chronic pain (N=48), compared to controls (N=42), which also revealed high levels of anthranilic acid and low levels of tryptophan in those with chronic pain.
The KYN pathway could serve as biomarkers that can help identify the risk of depression.