Mental health and substance use are inextricably linked. It is important to understand the definitions and common terms when talking about complex issues like opioids and the relationship between mental health and substance use. Mental health and behavioral health are often used interchangeably, but they are not quite the same.

Behavioral health—a more expansive term than mental health—refers to how things like daily cognitive habits affect a person’s overall well-being, emotions, biology, and behaviors. Mental health—a term that falls under the general umbrella of behavioral health—pertains to a person’s psychological state of being.

When talking about the opioid crisis, there are many common terms used to describe the problem. Here are some of the most common terms and definitions:

Terms

Drug misuse: The use of illegal drugs and/or the use of prescription drugs in a manner other than as directed by a doctor, such as use in greater amounts, more often, or longer than told to take a drug or using someone else’s prescription.

Naloxone: A drug that can reverse the effects of opioid overdose and can be lifesaving if administered in time. It is often sold under the brand name Narcan.

Nonmedical use: Taking prescribed or diverted prescriptions drugs (drugs not prescribed to the person using them) not in the way, for the reasons, in the amount, or during the time period prescribed.

Opioid dependence: Occurs when the body adjusts its normal functioning around regular opioid use. Unpleasant physical symptoms occur when medication is stopped.

Opioid tolerance: Occurs when a person using opioids begins to experience a reduced response to medication, requiring more opioids to experience the same effect.

Opioid use disorder (OUD): A problematic pattern of opioid use that causes significant impairment or distress. A diagnosis is based on specific criteria such as unsuccessful efforts to cut down or control use, or use resulting in social problems and a failure to fulfill obligations at work, school, or home, among other criteria. Opioid use disorder is preferred over other terms with similar definitions, “opioid abuse or dependence” or “opioid addiction”.

Overdose: Injury to the body (poisoning) that happens when a drug is taken in excessive amounts. An overdose can be fatal or nonfatal.

Substance misuse: The use of illegal drugs, prescription medications, or legal substances—such as alcohol—in a way that they are not meant to be used.

Substance use disorder: A disease that leads to compulsive use of a substance despite impaired physical, mental, and social function.