Sometimes patients diagnosed with a substance use disorder (i.e. drug addiction) also meet the criteria for another mental illness (e.g., a mood disorder or anxiety disorder). These patients are said to have co-occurring disorders or dual diagnosis disorders.
Dual diagnosis is common
According to the 2011 National Survey on Drug Use and Health, about 17.5% of American adults who met the criteria for a mental illness met the criteria for a substance use disorder as well. And among those with a serious mental illness, 22.6% reported past-year substance abuse or dependence. In clinical settings, these percentages can be much higher.
So, let us consider the causes and treatment of dual diagnosis disorders.
The causes of dual diagnosis
Three main mechanisms have been proposed.
One, mental illness may lead to substance abuse: Sometimes people with a mental health condition self-medicate using habit-forming drugs and, as a result, end up becoming addicted to them. To illustrate, some individuals with anxiety or insomnia who self-medicate with marijuana may develop cannabis use disorder (i.e. marijuana addiction).
Consider a second mechanism: Substance use could cause or exacerbate mental health conditions. For instance, cocaine use is associated with an increased risk of anxiety symptoms and panic attacks.
A third possibility is that mental illnesses and co-occurring substance use disorders are caused by similar factors or involve similar processes in the nervous system. We will use post-traumatic stress disorder (PTSD) as an example:
To manage their symptoms, a substantial portion of patients with PTSD abuse alcohol and other sedating drugs. However, drug abuse and PTSD also have certain neurological processes, like sensitization, in common. Specifically, just as the process of sensitization in substance use disorders sensitizes the user to the drug, sensitization in PTSD makes the individual more sensitive to, say, loud noises or other trauma-related stressors. In fact, sensitization is mediated by a brain region called the amygdala, which also processes fear- and stress-related stimuli.
Lastly, the high prevalence of dual diagnosis could be simply due to chance. Given the high rates of mental health conditions, is it really surprising that some individuals would meet the criteria for more than one psychiatric disorder at the same time?
The treatment of dual diagnosis disorders
A variety of medications and therapies are available for the treatment of substance use disorders and other psychological disorders. The effectiveness of some of these interventions for the treatment of co-occurring disorders is still under investigation.
In general, effective behavioral interventions for dual diagnosis disorders include five approaches, which are described below.
- Cognitive-behavioral therapy: Focuses on identifying, challenging, and replacing dysfunctional thoughts and maladaptive behaviors.
- Dialectical behavioral therapy: Teaches patients skills in interpersonal effectiveness, emotion regulation, mindfulness, and distress tolerance. This therapy modality is especially effective for reducing self-harm (e.g., suicidal behavior) and substance abuse.
- Contingency management: Uses rewards (e.g., privileges, vouchers exchangeable for goods, opportunities to win prizes) to promote positive change and healthy behaviors.
- Assertive community treatment: Provides individualized services (e.g., support, treatment, rehabilitation) to people with severe mental illness living in the community.
- Therapeutic communities: These drug-free residential settings facilitate the “resocialization” of patients with substance abuse, focusing on the community as the agent of change.
As for pharmacotherapy, occasionally the same medication may be used to treat both the substance use disorder and the other mental illness. To illustrate, bupropion (Wellbutrin) is approved for both tobacco use disorder and depression. In many cases, however, medications shown to be effective in treating a substance use disorder and ones effective for treating the co-occurring mental disorder are to be taken at the same time.