Treatment for addiction is always based, at least partly, on the assumption that deep emotional issues lie at the root of a substance abuse disorder. This is clearly true when OCD has been diagnosed, and an addiction recovery regimen that didn’t acknowledge and provide comprehensive treatment for a co-occurring obsessive-compulsive disorder would not be effective.
If the core causes of substance abuse are not tackled head on, relapse is virtually certain. At the same time even if it were possible to treat chemical dependency while leaving OCD unaddressed doing so would be a disservice to the patient, whose goal entering rehab is to return healthy and whole to a normal life.
The side effects of substance abuse tend to mimic those of mental illness in many instances, but that is not the case with OCD, which is a distinctive condition with clear warning signs. This makes it easier for a mental health professional to diagnose OCD even when chemical dependency is co-occurring.