What I Found in My Clients' Tests After Long COVID — And Why It Changes Everything — Finding #4: The Brain Chemistry Was Being Hijacked

Here is where it gets personal for anyone struggling with brain fog, low mood, anxiety, or sleep disruption after COVID. On the same OAT testing, quinolinic acid came back at the high ceiling of the reference range. To understand why that matters, I need to explain one pathway. COVID infection triggers a significant rise in a cytokine (inflammatory messenger) called IFN-&#947;. IFN-&#947; activates an enzyme called IDO1 , which hijacks tryptophan &#8212; the amino acid your body uses to make serotonin and melatonin &#8212; and redirects it toward a different chemical pathway. The downstream product of this hijacked pathway, when it runs too hard, is quinolinic acid . Quinolinic acid is a neurotoxin. It over-activates NMDA receptors in the brain, drives neuroinflammation, and generates oxidative damage in neurons. And simultaneously &#8212; because tryptophan is being diverted away from serotonin &#8212; the building material for serotonin itself is depleted. This is why SSRIs often fail in post-COVID neuropsychiatric symptoms. The drug is trying to make more use of serotonin that doesn&#8217;t exist, because the precursor &#8212; tryptophan &#8212; has been rerouted. The problem is upstream of where the medication acts. The OAT also showed pyroglutamic acid elevated &#8212; a marker of glutathione depletion, meaning the antioxidant defense system was under severe strain. The sy