Complex sentence: Low phenethylamine (PEA) concentration in the brain is associated with major depressive disorder, and high concentrations are associated with schizophrenia; low PEA levels and under-activation of TAAR1 also appears to be associated with ADHD.
Split into simpler sentences: Low phenethylamine (PEA) concentration in the brain is associated with major depressive disorder, and high concentrations are associated with schizophrenia. Low PEA levels and under-activation of TAAR1 also appears to be associated with ADHD.