Do we really choose our political beliefs?

This may be completely off topic but I think in general we don't take into account how much of a role our physical bodies play in our belief structures. For example, we all know that people are more irritable when they don't get enough sleep, or don't get enough to eat. Imagine what kind of effect that would have on your beliefs if you are consistently not getting enough sleep over long periods of time, or if you don't get regular meals. Also, illnesses have been known to really change people's personality. An extreme case of this is with Caligula, who went from competent Emperor to insane psychopath who believed he was a god after he recovering from an illness.