Our diet has a direct effect on our physical health. We all know this...
The same applies for our mental health. There is mounting evidence to suggest that our gut health is linked to various mental health conditions and the food that we eat can have both a positive and negative effect on our mood and ultimately, our thoughts and behaviours. I want to be very clear in saying that this is not to say it is necessarily the cause of these things but there are links that are currently being researched.
Some free information that may be interesting to you is available from these two sites.
http://overcomingdepressionandanxiety.com/