Agree with what already said and i also believe that a very low fat diet can lead to depression due to physiological changes when the body isnt getting enough fat..
I had a work colleague who lost a lot of weight..this was followed by her being off work unwell with depression for six long months ( i say long coz i had to cover her work in her absence!

)
This friend was a very contented person with a lovely lifestyle,happy marriage,good social life,very healthy etc..i knew her well enough to know this was true,not just a facade ..
She didnt have a lot of weight to lose but cut out all fat from her diet, and for first time in her life, suffered with depression.
I really think eating a fatfree diet can lead to depression even when day to day yr life is fulfilling in every way.