What you want to look into are "dual diagnosis" rehabs.
These are usually found in a hospital or psychiatric hospital, and their specific focus is addiction within mental illness, and usually, mental illness that requires medication. Which gets seriously tricky. As meds are still usually needed either in the short term or long term for their other diagnosis, as well as serious therapy, but the addiction also has to be treated.
The timeframe, as you can imagine, is rarely the 28 day program most rehabs are where people are only dealing with coming off drugs/alcohol. They tend a lot more towards being around the 3month range, and then IOP for several months following, but time frames vary a great deal. Someone who is misdiagnosed & on a screwed up cocktail of meds that should never be given together (or are the wrong meds for the disorder they have) may need to be weaned off, until they're absolutely sober, rediagnosed properly, and then new meds tried. Someone else may only need help with being actively suicidal for a few weeks during med rebound, or psychosis from insomnia, and then is best treated outpatient. So there is a whole lot of variability depending on what the actual dual-diagnosis is, and the patient's individual needs.
Similarly, the training the staff has at dual diagnosis clinics is astronomically better than at a standard rehab. To become a chemical dependency counselor is only a 3-6 month course. That's nowhere near enough to be dealing with anything beyond simply addiction. Which is why dual-diagnosis clinics don't employ chemical dependency counselors. They employ doctors, nurses, and social workers who also have their chemical dependency certification.
Dual Diagnosis. So you can treat both the addiction & PTSD.