Looking at BCAA research again. Interesting studies on brain chemistry.
In short, BCAAs compete with other large neutral amino acids into the brain. Taking it by itself lowers the percent of serotonin and dopamine precursors that make it through, thus lowering overall serotonin and dopamine.
Lowering serotonin is a good thing, but you want to promote dopamine as much as possible (within reason). If you stack BCAA with tyrosine, phenylalanine, or meat, only serotonin lowers while dopamine remains the same or increases. Effectively making it an anti-serotonin supplement.
Already put my order in for BCAA and l-phenylalanine. Read phenylalanine has broader anti-serotonin effects as well as promote dopamine. Too much tyrosine can go down the adrenaline path. Also came across couple studies suggesting you need sunlight (UV-A I think) for it to convert to dopamine.
All this is way more interesting and impactful than the marginal affect on muscle protein synthesis it gets hyped for. Especially with all the low key depression going on.