I have noticed that when i eat too much junk food my depression and anxiety get much worse than usual. is there a relation ?

Absolutely: Absolutely! There is definitely a link between foods that are high in sugar/fat and depression. Part of the reason is that the brain "knows" what's wrong and is trying to fix the neurochemical imbalance - so it looks for food to stimulate the positive mood producing neurotransmitters (in this case, dopamine primarily). Hope that helps!

Mind-body connection: Eating food that is not healthy for you can lower your energy, deprive your body of what it needs to run efficiently. This could cause a drop in mood due to the feeling of lethargy in your body. On the other hand, feeling bad about yourself for eating junk food, may also cause a lowering of mood. Could be you're getting a double dose of depressed mood.