I'm by no means an expert on this subject, but that article you linked is not trustworthy. It tells you to try fermented versions of soy instead of tofu, ostensibly to avoid the anxiety-inducing effects of tofu, and then later says fermented foods cause anxiety. It also gives a reason tofu causes anxiety as it contains compounds "that make the digestion of proteins incredibly difficult," but no rationale for how that causes anxiety. It also says copper is "linked to anxious behavior," a dubious claim, again with no source.
I'd ask your psychiatrist friend for some literature on the subject.