Your major absolutely doesn't matter to anyone but yourself. Pick something that fascinates you.
Well-rounded intellectual experiences help you become a well-rounded person, and this indirectly helps you become a well-rounded psychiatrist, and, later, a grown-up psychiatrist who doesn't get burnt out or overly narrow, but there is little in an introductory psych or anthro or sociology class that you'll directly use in psychiatry training. Not that it hurts, but you shouldn't pick your course of study based on that. If you love French lit or neuroscience or birds, then study one of those things. You'll enjoy yourself, make better grades, and will impress various admissions committees with your level of enthusiastistic curiosity--remember, they anticipate teaching you what you need to know.
Beyond that, it is very useful to learn how to write (ie, to learn how to think).