Lack of Motivation and Vitamins

Patient: I am experiencing lack of motivation and feelings of worthlessness. They are becoming more prominent so I have started examining possible causes. I have felt this way before on various medicines but I am not currently taking any medication except for a vitamin supplement. I started taking Fish Oil and vitamin B6 together a few weeks ago to improve focus. I do not take them regularly due to forgetfulness. Could the vitamins be the cause?

Symptoms: Lack of motivation; Feelings of worthlessness; depression; lack of appetite