Dual Diagnosis as the Co-Occurrence of Substance Use Disorder and Another Psychiatric Condition

Not Just the Sum of Diagnoses

Dual diagnosis most commonly involves a combination of alcohol or other substance dependence with depression, anxiety disorders, or psychotic illness. In clinical practice, however, this is not merely the “sum” of two diagnoses, but rather a condition in which both disorders mutually influence and exacerbate each other. The question of which came first –⁠ the addiction or the psychiatric disorder –⁠ is often unanswerable and ultimately secondary when choosing a treatment strategy.

Epidemiological studies from recent years indicate that the prevalence of dual diagnosis among children and adolescents treated for psychiatric conditions ranges between 18% and 54%. The co-occurrence of substance use disorder and psychiatric illness is therefore a common clinical reality rather than an exception.

What the Data Show

Patients with dual diagnosis belong to the highest-risk groups within the healthcare system. Not because they are noncompliant, but because they are often exposed to fragmented care. The consequences of this approach were examined in a recent meta-analysis published in Journal of Dual Diagnosis.

The authors analyzed 13 controlled studies conducted between 2001 and 2024, comprising more than 100,000 patients. They compared treatment outcomes in individuals with dual diagnosis and in patients with a single diagnosis –⁠ either psychiatric or substance-related.

The results are unequivocal. Patients with dual diagnosis had a 71% higher risk of adverse treatment outcomes compared with those with a single diagnosis (RR 1.71; 95% CI 1.38–2.13). In other words, under the current model of care, these patients are nearly twice as likely to experience unfavorable clinical outcomes, including relapse, repeated hospitalization, and mortality. This finding was consistent across studies.

Interestingly, differences between groups were small or absent with respect to symptom severity and psychosocial indicators. This suggests that standard treatment may temporarily alleviate symptoms but fails in areas that truly matter –⁠ relapse prevention, acute crisis management, and mortality reduction. The authors also point out that most evaluated programs focused on only one component of the disorder, whereas truly integrated treatment was rather the exception.

Integrated Care as a Necessity

The Czech context tends to confirm rather than contradict this situation. Recent professional publications highlight that research on dual diagnoses in the Czech Republic remains insufficient and that systematic data are lacking. They also emphasize the diagnostic complexity of these conditions and the absence of standardized procedures that would allow timely identification and coordinated treatment. Czech clinical practice therefore still relies primarily on international evidence.

These realities are reflected in clinical recommendations. International guidelines, including updated British NICE guidelines for patients with coexisting mental illness and substance use, stress the necessity of coordinated care and warn against separating psychiatric and addiction treatment. The recommendations emphasize ongoing assessment of both components of the disorder and discourage excluding patients from care simply because their difficulties extend beyond the scope of a single specialty.

In this light, the results of the meta-analysis are not surprising but rather confirm long-standing clinical experience. Recurrent relapse or rehospitalization in patients with dual diagnosis is not a failure of the individual, but a consequence of a system that treats both disorders separately instead of addressing them as a single clinical entity. An integrated approach is therefore not a matter of preference but of necessity.

Editorial Team, Medscope.pro

Sources:

1. Scott K. D., Gorey K. M. Concurrent disorders and treatment outcomes: A meta-analysis. J Dual Diagn 2025;21(3):251–265, doi: 10.1080/15504263.2025.2515015.
2. Tomáš J., Šťastná L. Prevalence of dual diagnoses among children and adolescents with mental health conditions. Children (Basel) 2023;10(2):293, doi: 10.3390/children10020293.
3. Varyšová L., Šťastná L. Dual disorder –⁠ how (non)uniform terminology influences research, diagnosis, and treatment. Čes Slov Psychiatr 2025;121(5):230–237.
4. Dual diagnosis. Závislosti Olomouc. Available at: https://zavislostiolomouc.cz/blog/dualni-diagnoza