B vitamins have an effect on the nervous system. For example the mega-dose of B6 (or P5P) that can help with autism can lead to difficulty moving the legs and walking. The effect is temporary and reversed when discontinuing. (I'm paraphrasing from the 1987 study by Bernard Rimland.)

A sudden drop in blood sugar can bring about anxiety. I experience this a few hours after going to bed if I've over indulged in sweets before going to bed. Maybe alcohol has the same effect.