Addiction and Recovery: Xanax

Xanax adddiction. Does anyone know anything about it? My neighbor John, has been treated by a doctor for panic attacks for a couple of years with xanax. Once in a while, the Doctor would up the dosage to make it more effective.  Now things have settled down in John’s life and the Doctor has tappered John off the drug, but he is not the same old guy that I knew before he stopped xanax. Any Ideas?