Addiction (including alcoholism) is a primary, progressive, chronic disease with genetic, psychosocial, and environmental factors influencing its development and manifestations.
It is progressive and often fatal.
It is characterized by impaired control over use of the substance, preoccupation with the substance, use of the substance despite adverse consequences, and distortions in thinking.
It is compulsive use of a substance without regard to negative consequence.
There is also the presence of tolerance, meaning more and more of the substance is necessary to achieve the same effect and withdrawal that is the result of physical dependence. This can be things such as seizures, flu-like symptoms, sleep disturbances, and depression, depending on the substances used.
It is classified as a disease as it shares characteristics of many other chronic diseases.
The substances cause biochemical and structural changes in the brain, which reinforce use. Depending on the substance this can occur relatively quickly or over longer periods of time.