People with mental health disorders are more likely than people without mental health disorders to experience an alcohol or substance use disorder. Co-occurring disorders can be difficult to diagnose due to the complexity of symptoms, as both may vary in severity. In many cases, people receive treatment for one disorder while the other disorder remains untreated. This may occur because both mental and substance use disorders can have biological, psychological, and social components. Other reasons may be inadequate provider training or screening, an overlap of symptoms, or that other health issues need to be addressed first. In any case, the consequences of undiagnosed, untreated, or undertreated co-occurring disorders can lead to a higher likelihood of experiencing homelessness, incarceration, medical illnesses, suicide, or even early death.

People with co-occurring disorders are best served through integrated treatment. With integrated treatment, practitioners can address mental and substance use disorders at the same time, often lowering costs and creating better outcomes. Increasing awareness and building capacity in service systems are important in helping identify and treat co-occurring disorders. Early detection and treatment can improve treatment outcomes and the quality of life for those who need these services.