Abstract: Described herein are methods of identifying, characterizing, and treating depression and anxiety in a subject by modulating indoles associated with tryptophan metabolism in the subject and subject's gut microbiome.

Abstract: Described herein are methods and compositions for diagnosing and evaluating the treatment of depression using one or more biomarker metabolites for the diagnosis and monitoring treatment efficacy. In one aspect, the biomarker metabolites comprise bile acids and can be used to screen subjects for the likelihood of developing depression or anxiety, the diagnosis thereof, monitoring the efficacy of treatment, and evaluating a subject's propensity for responding to treatment.