regress vs go back

regress is a noun but go back is not a noun.

Word	Noun	Adjective	Verb	Adverb
regress	Yes	No	Yes	No
go back	No	No	Yes	No

As verbs, go back is a hyponym of regress; that is, go back is a word with a more specific, narrower meaning than regress:

Other hyponyms of regress include fall back, lapse, recidivate, regress, relapse, retrogress, resile, recover, recuperate.

regress (noun)	go back (noun)
returning to a former state
the reasoning involved when you assume the conclusion is true and reason backward to the evidence

regress (verb)	go back (verb)
go back to bad behavior	regain a former condition after a financial loss
get worse or fall back to a previous condition	return in thought or speech to something
go back to a previous state	belong to an earlier time
go back to a statistical means