The only program available to shorten a federal inmate's sentence is RDAP, Residential Drug Abuse Program. An inmate who successfully completes that rigorous program can have a year knocked off his or her sentence. This is the only time I know where being an addict is a benefit.
I have heard that the program can be very good and I am glad for the inmates who do benefit from it.
Inmates who do not abuse drugs or alcohol have no comparable way to shorten their sentences.
During my husband's pre-sentencing interview, he was encouraged to claim a substance abuse problem; the person doing the interview even prodded a little to see if he wanted to claim a problem with prescription drugs. At the time, we thought it odd that they were pushing him to say something untrue. If we had known, would we have tried to gin up a good story about alcoholism?
No, we would not.