Dual diagnosis is a term for when someone experiences a mental illness and a substance abuse problem simultaneously. Dual diagnosis is a very broad category. It can range from someone developing mild depression because of binge drinking, to someone’s symptoms of bipolar disorder becoming more severe when that person abuses heroin during periods of mania.
Either substance abuse or mental illness can develop first. A person experiencing a mental health condition may turn to drugs and alcohol as a form of self-medication to improve the troubling mental health symptoms they experience.
Research shows though that drugs and alcohol only make the symptoms of mental health conditions worse. Abusing substances can also lead to mental health problems because of the effects drugs have on a person’s moods, thoughts, brain chemistry and behavior.
See more at: NAMI.org