What Causes Agitation And Disorientation While On Hydromorphone?

My 93 year old mother was put on .25m of hydromorphone 3/day mid sept. By the end of Oct I noticed problems with her short term memory. This has gotten progressively worse over time. Just after Christmas her dosage was upped due to her pain. She is now very agitated, disorientated and thinks she is still living with my Dad who passed away 32 years ago. I have asked the nurse practitioner if the hydro morphine could be causing this. Do you think we should take her off it?