You are what you eat, or perhaps more accurately, you feel what you eat.  Research continues to show that at a specific nutrient contained in fish can help alleviate depression. The nutrient is an omega-3 fatty acid called EPA.

Healthy brains and nerve cells depend on omega-3s because the nervous system is made mostly of fat.  The fats that you eat influence the composition of your brain cells. Unlike many nutrients omega-3 fatty acids are not produced by our bodies.  Fish are an excellent source.

And if you don't like fish, you can also get your fill from walnuts or flaxseed.