It's true to say high Phe levels affect your mood, phenylalanine is metabolised into Tyrosine which itself is a precourser for a number of other hormones including, adrenaline, noradrenalin &amp; melanin responsible to skin/eye/hair colour, another is dopamine which is a neurotransmitter directly associated with motor control and mood. I actualy take extra Tyrosine as a supplement as there has been research into it's affect on the blood brain barrier and there is substantial proof that higher levels of tyrosine in the blood actually blocks the amount of phenylalanine able to cross into the brain. I do falter though and have succombed to anti-depressant drugs which seemed to just add to my complications, recently I've just lost my partner, home and my job because of a dramatic change in my personality due to being prescribed anti-depressant for what I considered maybe just a bit of discontent. G.P.s in the UK dish out these drugs willy nilly and I am sure they just add fuel to fire in most cases. So it seems that my only way to deal with life is to maintain a strict low phe diet for which I need to be well organised, motivated and focused, all the things I don't have because of my PKU.