Substance use falls on a continuum based on frequency, intensity, and degree of dependency. Some substances, like alcohol, have recognized health benefits when used in moderation, but can be extremely harmful when used in excess (even occasionally) or when use becomes addictive. The transition from use that may be "normal" or "minimal risk," to use that is problematic can be a slow, gradual process, and is not an inevitability. Alternatively, problem substance use can occur more quickly, such as heavy drinking following a relationship loss, or increased dependence on pain medications following an accident. Addiction, the most serious level of substance use, is a disorder identified with loss of control, preoccupation with disabling substances, and continued use or involvement despite negative consequences.
The problems that can develop from substance misuse vary from mild to severe, and can involve a multitude of life functioning areas. Problems experienced from substance use can include immediate consequences such as a hangover following a night of excessive alcohol consumption. And as substance use becomes more problematic, individuals can experience larger losses such as legal consequences, job loss, health problems, relationship problems or increased debt. How quickly substance use becomes problematic depends on the individual, their behaviour, and factors within physical, psychological, economic, spiritual, social, and legal contexts.
The personal costs of an addiction may include a job, a family, an education and the ability to participate in social activities and community events. Without appropriate income and community-support services, people with substance use problems can become trapped in a "revolving door syndrome." Once released from hospital or residential treatment, many people with addictions are forced to resort to substandard housing because of a lack of money. In turn, their health deteriorates, resulting in return visits to the hospital or treatment centre and an increase in the symptoms of their mental illness, or a relapse. The stress of poverty increases a person's vulnerability to substance use problems, resulting in even more challenges to recovery.