The term “dual diagnosis” describes the clinically challenging comorbidity of a substance use disorder (SUD) along with another major mental illness. Based on data from the Epidemiologic Catchment Area study, the lifetime prevalence of SUDs among patients with mental illness is approximately 30%, and is higher among patients with certain mental disorders, such as schizophrenia (47%), bipolar disorder (61%), and antisocial personality disorder (84%).1 These statistics highlight that addiction is often the rule rather than the exception among those with severe mental illness.1 Not surprisingly, the combined effects of having an SUD along with another mental illness are uniformly negative (Table 12-4).
Based on outcomes research, the core tenets of evidence-based dual-diagnosis treatment include the importance of integrated (rather than parallel) and simultaneous (rather than sequential) care, which means an ideal treatment program includes a unified, multidisciplinary team whose coordinated efforts focus on treating both disorders concurrently.2 Evidence-based psychotherapies for addiction, including motivational interviewing, cognitive-behavioral therapy, relapse prevention, contingency management, skills training, and/or case management, are a necessity,3,5 and must be balanced with rational and appropriate pharmacotherapy targeting both the SUD as well as the other disorder (Table 22,3,5-9).
3 ‘Real-world’ clinical challenges
Ideal vs real-world treatment
Treating patients with co-occurring disorders (CODs) within integrated dual-disorder treatment (IDDT) programs sounds straightforward. However, implementing evidence-based “best practice” treatment is a significant challenge in the real world for several reasons. First, individuals with CODs often struggle with poor insight, low motivation to change, and lack of access to health care. According to the Substance Abuse and Mental Health Services Administration (SAMHSA), 52% of individuals with CODs in the U.S. received no treatment at all in 2016.10 For patients with dual disorders who do seek care, most are not given access to specialty SUD treatment10 and may instead find themselves treated by psychiatrists with limited SUD training who fail to provide evidence-based psychotherapies and underutilize pharmacotherapies for SUDs.11 In the setting of CODs, the “harm reduction model” can be conflated with therapeutic nihilism, resulting in the neglect of SUD issues, with clinicians expecting patients to seek SUD treatment on their own, through self-help groups such as Alcoholics Anonymous or in other community treatment programs staffed by nonprofessionals that often are not tailored to the unique needs of patients with dual disorders. Psychiatrists working with other mental health professionals who provide psychotherapy for SUDs often do so in parallel rather than in an evidence-based, integrated fashion.
IDDT programs are not widely available. One study found that fewer than 20% of addiction treatment programs and fewer than 10% of mental health programs in the U.S. met criteria for dual diagnosis–capable services.12 Getting treatment programs to become dual diagnosis–capable is possible, but it is a time-consuming and costly endeavor that, once achieved, requires continuous staff training and programmatic adaptations to interruptions in funding.13-16 With myriad barriers to the establishment and maintenance of IDDTs, many patients with dual disorders are left without access to the most effective and comprehensive care; as few as 4% of individuals with CODs are treated within integrated programs.17
Diagnostic dilemmas
Establishing whether or not a patient with an active SUD has another serious mental illness (SMI) is a crucial first step for optimizing treatment, but diagnostic reliability can prove challenging and requires careful clinical assessment (Table 3). As always in psychiatry, accurate diagnosis is limited to careful clinical assessment18 and, in the case of possible dual disorders, is complicated by the fact that both SUDs as well as non-SUDs can result in the same psychiatric symptoms (eg, insomnia, anxiety, depression, manic behaviors, and psychosis). Clinicians must therefore distinguish between:
- Symptoms of substance intoxication or withdrawal vs independent symptoms of an underlying psychiatric disorder (that persist beyond a month after cessation of intoxication or withdrawal)
- Subclinical symptoms vs threshold mental illness, keeping in mind that some mood and anxiety states can be normal given social situations and stressors (eg, turmoil in relationships, employment difficulties, homelessness, etc.)
- Any mental illness (AMI) vs SMI. The latter is defined by SAMHSA as AMI that substantially interferes with or limits ≥1 major life activities.10
With these distinctions in mind, data from the 2016 National Survey on Drug Use and Health indicate that dual-diagnosis comorbidity was higher when the threshold for mental illness was lower—among the 19 million adults in the U.S. with SUDs, the past-year prevalence was 43% for AMI and 14% for SMI.10 Looking at substance-induced disorders vs “independent” disorders, the 2001-2002 National Epidemiologic Survey on Alcohol and Related Conditions found that for individuals with SUDs, the past-year prevalence of an independent mood or anxiety disorder was 35% and 26%, respectively.19 Taken together, these findings illustrate the substantial rate of dual-diagnosis comorbidity, the diagnostic heterogeneity and range of severity of CODs,20 and the potential for both false negatives (eg, diagnosing a substance-induced syndrome when in fact a patient has an underlying disorder) and false positives (diagnosing a full-blown mental illness when symptoms are subclinical or substance-induced) when performing diagnostic assessments in the setting of known SUDs.
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