Dual diagnosis or co-existing conditions (also known as comorbid conditions or concurrent disorders) are common in those with substance abuse issues. A dual diagnosis is where there is a mental illness such as major depressive disorder, social anxiety disorder, or schizophrenia present along with the substance use disorder.
Addictions and other mental illnesses are closely linked. One-in-four adults living with a serious mental illness develop substance use disorders, and it is known that 1) substance abuse increases a person’s risk for another mental illness and 2) another mental illness increases a person’s risk of drug abuse.
It is not known why addiction and other mental illnesses are so closely related but it is likely a combination of the following three factors:
- Drugs of abuse can cause users to experience psychiatric symptoms, such as the experience of psychosis with cannabis use.
- When one suffers from a mental illness such as an anxiety disorder, that person may be tempted to self-medicate using a drug. For example, it has been shown that up to 90% of people with schizophrenia smoke, and this appears to lessen some symptoms of the disease as well as improve cognition.
- Addiction disorders and mental illnesses appear to share common roots such as genetic vulnerability, underlying brain defects, and early exposure to stress or trauma.