Can any doc explain why can't i take narcotics with anti-anxiety and anti-depressants?

Drug interactions: You can take narcotics with anti-anxiety medications. But some anti-anxiety medications such as benzodiazepine (valium, clonapin) may potentiate the respiratory depressant effects of narcotics. Also there are some interactions between some narcotics and antidepressants. Most prominent is the one between Demerol (meperidine hydrochloride) and maois. Neither of these are commonly used.