Xanax is a benzo that some doctors use for depression. They do make you sleepy, the bottle usually states not to take while driving or doing hazardous tasks . 3x / day seems like a pretty high dose to start but maybe your husband can handle it. If you notice a change in him, such as mood disorder, short temper, etc. it should be reported to your doctor. I have to wonder why the doctor didn't prescribe a regular antidepressant instead of an anxiolitic? Xanax is often used as an adjunct with other meds for seizures.
I'm sure your doctor had his reasons for prescribing them, too bad he didn't explain.