Tryptophan depletion predicts lower positive affect in sexual minority men living with HIV who use methamphetamine

This longitudinal study with 76 sexual minority men living with HIV who use methamphetamine examined whether dysregulation of essential amino acid precursors for neurotransmitters at baseline predicted positive and negative affect at 15 months. After controlling for covariates including baseline positive affect, a higher baseline kynurenine/tryptophan (K/T) ratio independently predicted lower positive affect at 15 months ( β = − 18.31; 95% CI = − 35.35, − 1.27; p = 0.036). Future clinical research should examine whether bio-behavioral interventions targeting tryptophan degradation could optimize treatments for people living with co-occurring HIV and stimulant use disorders.