Substance use disorder (SUD) is the persistent use of drugs (including alcohol) despite substantial harm and adverse consequences. Substance use disorders are characterized by an array of mental/emotional, physical, and behavioral problems such as chronic guilt; an inability to reduce or stop consuming the substance(s) despite repeated attempts; driving while intoxicated; and physiological withdrawal symptoms. Drug classes that are involved in SUD include: alcohol; cannabis; phencyclidine and other hallucinogens, such as arylcyclohexylamines; inhalants; opioids; sedatives, hypnotics, or anxiolytics; stimulants; tobacco; and other or unknown substances.
In the Diagnostic and Statistical Manual of Mental Disorders 5th edition (2013), also known as DSM-5, the DSM-IV diagnoses of substance abuse and substance dependence were merged into the category of substance use disorders. The severity of substance use disorders can vary widely; in the DSM-5 diagnosis of a SUD, the severity of an individual’s SUD is qualified as mild, moderate, or severe on the basis of how many of the 11 diagnostic criteria are met. The International Classification of Diseases 11th revision (ICD-11) divides substance use disorders into two categories: (1) harmful pattern of substance use; and (2) substance dependence.
In 2017, globally 271 million people (5.5% of adults) were estimated to have used one or more illicit drugs. Of these, 35 million had a substance use disorder. An additional 237 million men and 46 million women have alcohol use disorder as of 2016. In 2017, substance use disorders from illicit substances directly resulted in 585,000 deaths. Direct deaths from drug use, other than alcohol, have increased over 60 percent from 2000 to 2015. Alcohol use resulted in an additional 3 million deaths in 2016.
According to Statistics Canada (2018), approximately one in five Canadians aged 15 years and older experience a substance use disorder in their lifetime. In Ontario specifically, the disease burden of mental illness and addiction is 1.5 times higher than all cancers together and over 7 times that of all infectious diseases. Across the country, the ethnic group that is statistically the most impacted by substance use disorders compared to the general population are the Indigenous peoples of Canada. In a 2019 Canadian study, it was found that Indigenous participants experienced greater substance-related problems than non-Indigenous participants.
Statistics Canada’s Canadian Community Health Survey (2012) shows that alcohol was the most common substance for which Canadians met the criteria for abuse or dependence. Surveys on Indigenous people in British Columbia show that around 75% of residents on reserve feel alcohol use is a problem in their community and 25% report they have a problem with alcohol use themselves. However, only 66% of First Nations adults living on reserve drink alcohol compared to 76% of the general population. Further, in an Ontario study on mental health and substance use among Indigenous people, 19% reported the use of cocaine and opiates, higher than the 13% of Canadians in the general population that reported using opioids.