I don't think most universities really care how 'diverse' your subjects are, especially for a science course (since a lot of universities say stuff like "We want an A level in X science, and one in maths, blah blah" so they usually seem to regard multiple sciences as good (it shows your passions clearly lie within the science subjects).
And not to upset psychology people but is it really considered a science by universities? o.O It's essay based and mostly about case studies from what I hear, my school doesn't list it with the other science subjects, so it's not really /that/ sciencey in the first place.