In a sense, the difficulty with treating co-occurring disorders can be categorized as an ordering problem: Which do you treat first? The contemporary answer is, "Both." Such an approach is called a dual-diagnosis approach. A dual-diagnosis approach readily acknowledges the inter-relationship between dual disorders so that both conditions are addressed simultaneously. The therapist works to help the client understand this inter-relationship as well.
Here is an example of how a dual-diagnosis approach to therapy might be conducted. Suppose a client has an Alcohol Use Disorder and also has a Borderline Personality Disorder. Treatment would address the problems associated with excessive drinking and the problems associated with Borderline Personality Disorder. This will typically include interpersonal difficulties, impulsivity, self-destructive behaviors, and emotional dys-regulation. Furthermore, the relationship between the two sets of problems would be addressed. The therapy participant is assisted to understand how one set of problems leads to, or worsens the other set of problems, and vice versa. Continuing with our example, someone with Borderline Personality Disorder might drink in order to cope with very intense emotions. The person would be guided to understand that while alcohol "solves" one set of problems (emotional regulation) it leads to another set of problems because alcohol consumption causes poor judgment and disinhibition thereby worsening the other set of problems of the Borderline Disorder (impulsivity, self-destructive behaviors, interpersonal conflict).
Through a dual diagnosis treatment approach, the therapy participant begins to recognize that while alcohol may solve the immediate problem of regulating intense emotion, it only worsens the other problems associated with the Borderline Disorder; in effect, solving nothing. When understood from this integrative, "dual" perspective, it becomes easier to make the wiser choice not to drink. Moreover, the therapy participant would need to rapidly learn better ways to manage emotions since this symptom underlies the problem drinking. For instance, some of the emotional regulation and distress tolerance skills taught in the Dialectical Behavior Therapy modules would be very beneficial. Meanwhile, the therapist and the client would simultaneously work on strategies and techniques to discontinue drinking. This might include increasing social support, perhaps through a program such as Alcoholics Anonymous; participation in stress reduction activities such as yoga, and learning relapse prevention skills.
In summary, acute, high-risk behaviors must be addressed first. Once stabilized, a dual-diagnosis approach designed to treat both disorders simultaneously provides the most effective approach for treating co-occurring disorders.