Are the following sentences grammatically correct?
- He asked me if I was depressed the day before.
- He asked me if I had been depressed the day before.
Please explain. Thanks!
Both are correct. Some speakers will "backshift" the tense in the reported speech, while others will not. There is no requirement to do so.
"yesterday" must be the preterite, when it comes to "the day before", preterite and past perfect tenses are right. The phrase of "had been" stress the procedure.