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It sounds as though the antidepressant they've chosen for him is not working. Help him get back to a psychiatrist to see if adding Abilifiy will help the Zoloft work better, or if it's time to switch him to another antidepressant. It can be hard to know which one a person's depression will respond to, so it may take a couple of changes to get the exact medication and dosage that will help. Also it would be good to help him find a therapist to talk to while he's waiting to go back into rehab. Make sure the therapist is certified to treat addictions, and specializes in this kind of work.