The term “dual disorder” (DD) refers to the coexistence or concurrence of at least one substance use disorder (SUD) and another mental disorder in the same person, as the World Health Organization established in its lexicon of alcohol and drug terms. At the beginning of the last decade, the World Psychiatric Association (WPA) created a new section for this topic, deciding to use the term dual disorder/pathology.

DD has been associated with a worse prognosis in affected people. Compared with patients with a single disorder, SUD or another psychiatric disorder, patients with DD show greater psychopathological severity, greater attendance at emergency services, as well as a higher frequency of psychiatric admissions and a higher prevalence of suicide. In addition, DD patients present more risk behaviors, which are linked to infections like HIV and hepatitis B and C, as well as to unemployment, homelessness and illegal behaviors. Thus, taking into account the burden it places on the health and legal systems, psychiatric comorbidity among persons who use drugs carry high costs for society. Studies have shown that comorbid disorders are reciprocally interactive and cyclical, and a poor prognosis can be expected for both SUD and other mental disorders if treatment does not address DD in an integrated way...

See also, other articles from this special issue on dual diagnosis:

• The Tryptophan System in cocaine-induced depression
• DRD4, DRD2, DAT1, and ANKK1 genes polymorphisms in patients with dual diagnosis of polysubstance addictions
• Health-related quality of life in male patients under treatment for substance use disorders with and without major depressive disorder: influence in clinical course at one-year follow-up
• The relevance of dual diagnoses among drug-dependent patients with sleep disorders
• Alcohol induced depression: clinical, biological and genetic features
• Traumatic events in dual disorders: prevalence and clinical characteristics
• Childhood trauma predicts less remission from PTSD among patients with co-occurring alcohol use disorder and PTSD
• Sleep quality and sleep disturbance perception in dual disorder patients
• Temperament and character profile and its clinical correlates in male patients with dual schizophrenia
• Cannabis use, cannabis use disorder, and comorbid psychiatric illness: a narrative review
• Concurrent disorder management guidelines. systematic review
• The conceptual framework of dual disorders and its flaws