Here the finding is that younger individuals with the A- trait gene have lower parasympathetic tone and higher anxiety while older indivduals without the A- trait gene have the lower parasympathetic tone and higher anxiety. Not sure how much of this is environmentally confounded.
But perhaps the unmeasured genes for parasympathetic tone are confounding also. That is, those without N trait may be unusual among the Han Chinese in this population but may be affecting the result since those without N trait (having low parasympathetic tone) having A- trait would be extremely rare according to NPA theory and almost surely would have schizophrenia and be institutionalized. Or they could possibly be N-PA- or -NPA- or similar genotypes. And those without A- trait with low parasympathetic tone could be A or PA types?
So since higher anxiety is related to P trait and to A- trait as well as N- or -N trait, the COMT gene would be not the only gene related to anxiety?