Dual diagnosis occurs when an individual has both a mental health disorder and a substance use disorder at the same time. This combination can make diagnosis and treatment more complex because each condition can influence and exacerbate the other. For instance, someone with depression may turn to alcohol or drugs as a form of self-medication, which can worsen their mental health symptoms. Common dual diagnoses include depression with alcohol addiction, anxiety with drug abuse, or schizophrenia with substance dependency. Effective treatment for dual diagnosis often involves integrated care, combining therapy, medication, and support to address both issues simultaneously and help individuals recover holistically.