those two fields...unlikely unless you took the time to complete residencies in both which would be a waste of time. There are some combined residency programs but the fields are usually more similar (e.g. psych/neuro, or peds/psych. See: https://www.acgme.org/ads/Public/Rep...micYearId=2012
). A faculty member at my school was double board certified in medicine and pathology but i'm pretty sure he did that on his own.
Unless you're in medical school it's too early to worry about what specialty exactly anyway.