That’s a very good question, which (like many good questions) doesn’t really have a clear answer. If a psychologist can win the Nobel Prize for Economics, it’s obvious that there is more than a passing connection between the two.

In my view there is little progress to be made by trying to establish definite boundaries between the social sciences: they all attempt to understand, predict and influence human behaviour. If you take an empirical, evidence-based perspective the exact label of the discipline doesn’t matter that much; what matters is that what you do enhances understanding and insight, and fits the facts.