What are the differences between drug-induced and co-occurring depression?

Many substances can cause symptoms similar to depression during their use or during withdrawal from their use.  Some substances, such as methamphetamine, may have a prolonged effect on mood even long after someone stops taking the drug. In general, a co-occurring mood disorder such as depression will persist after a person has been abstinent for an extended period of time. Also, the person often will have experienced symptoms prior to starting use of alcohol or other drugs. A qualified professional can help make the distinction and suggest the appropriate treatments.