What is the relationship between mental illness and substance abuse ?

Addictions can also be a significant cause of mental illness. This addictions produce changes in normal behavior , desires, priorities and abilities.

The consumption of this substances, such as alcohol or other drugs, may originate symptoms of anxiety, depression or even paranoia. For example, people under the effect of marijuana can experience delusions and develop psychosis. Also when they have a lack of the drug they are using, they may behave aggressively or in an anxious way.

As a matter of fact, those who suffer a mental illness are more likely to take drugs. For example, people with depression may "self-medicate" themselves with alcohol or other drugs.