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Addiction | Definitions


A chronic, relapsing disease characterized by compulsive drug seeking and abuse in spite of known adverse consequences, and by functional, sometimes long-lasting changes in the brain.

Antisocial Personality Disorder

A disorder characterized by antisocial behaviours that involve pervasive disregard for and violation of the rights, feelings, and safety of others, beginning in childhood or the early teenage years and continuing into adulthood.

Attention-Deficit Hyperactivity Disorder (ADHD)

A disorder characterized by inattentiveness and/or hyperactivity and impulsivity at a level far greater than others of the same age.

Anxiety Disorders

Varied disorders that involve excessive or inappropriate feelings of anxiety or worry. Examples are panic disorder, post-traumatic stress disorder, social phobia, and others.

Bipolar Disorder

A mood disorder characterized by alternating episodes of depression and mania or hypomania.


The occurrence of two disorders or illnesses in the same person, at the same time (co-occurring comorbid conditions)


A chemical (neurotransmitter) found in parts of the brain responsible for the regulation of reward, motivation, and movement.

Dual Diagnosis/Mentally Ill Chemical Abuser (MICA)

Other terms used to describe the comorbidity of a drug use disorder and another mental illness.


A disorder marked by sadness, inactivity, difficulty with thinking and concentration, significant increase or decrease in appetite and time spent sleeping, feelings of dejection and hopelessness, and sometimes, suicidal thoughts or an attempt to commit suicide.

Major Depressive Disorder

A mood disorder having a clinical course of one or more serious depression episodes that last two or more weeks. Episodes are characterized by a loss of interest or pleasure in almost all activities; disturbances in appetite, sleep, or psychomotor functioning; a decrease in energy; difficulties in thinking or making decisions; loss of self-esteem or feelings of guilt; and suicidal thoughts or attempts.


A mood disorder characterised by abnormally and persistently elevated, expansive, or irritable mood; mental and physical hyperactivity; and/or disorganization of behaviour. Lasting at least one week or less if hospitalisation is necessary.

Mental Disorder

A mental condition marked primarily by sufficient disorganization of personality, mind, and emotions to seriously impair the normal psychological or behavioural functioning of the individual. Addiction is a mental disorder.


The brain’s chemical messengers used to transmit information between neurons.

Post-Traumatic Stress Disorder (PTSD)

A disorder that develops after exposure to a highly stressful event (e.g., wartime combat, physical violence, or natural disaster). Symptoms include re-experiencing the trauma through flashbacks or recurrent nightmares, hypervigilance and difficulty sleeping, and avoidance of reminders of the event.


A serious mental disorder (e.g., schizophrenia) characterized by defective or lost contact with reality. Symptoms often include hallucinations or delusions.


A psychotic disorder characterized by symptoms that fall into two categories: (1) positive symptoms, such as distortions in thoughts (delusions), perception (hallucinations), and language and thinking and (2) negative symptoms, such as flattened emotional responses and decreased goal-directed behaviour.


The use of a substance to lessen the negative effects of stress, anxiety, or other mental disorders (or side effects of their pharmacotherapy). Self-medication may lead to addiction and other drug- or alcohol-related problems.