Opioid use disorder is a chronic disease of the brain—sometimes called a mental disorder—characterized by the persistent use of opioids in spite of the deleterious effects it has on one’s health and social relationships. People with opioid use disorder typically have both physical and psychological dependence; this often has serious health consequences. People with opioid use disorder are at high risk of relapse; if someone with the disorder stops using opioids, even after years of abstinence, they are at increased risk of reverting to opioid use. Opioid use disorder is diagnosed based on certain criteria; if someone with OUD experiences at least two of the following signs and symptoms within the past 12-month period, the diagnosis is confirmed: ⦁ Physical dependence: ⦁ Developing tolerance to opioids, meaning that larger quantities of the drug are needed to attain the same effect ⦁ Experiencing withdrawal symptoms if stopping opioid use ⦁ Using opioids to alleviate symptoms of withdrawal ⦁ Loss of control: ⦁ Taking opioids in greater quantities or for longer periods than originally planned or prescribed ⦁ Inability to quit or reduce the use of opioids despite a desire to do so ⦁ Investing a significant amount of time to the acquisition, use, or recovery from opioids; constantly thinking about opioids and planning the next use ⦁ Feeling compelled to use opioids ⦁ Consequences: ⦁ Opioid use repeatedly causes disruptions and difficulties performing duties at home, work, or school ⦁ Continuing use of opioids even when they have a damaging effect on social interactions and relationships ⦁ Missing important events or occasions in personal life or at work or school, either intentionally or unintentionally ⦁ Repeatedly taking opioids in situations that could result in physical harm to self or others, such as while operating a motor vehicle or working with hazardous materials ⦁ Continuing use of opioids even when they create or aggravate problems affecting physical and mental health While not everyone who misuses opioids will experience all of the aforementioned signs, the more signs or symptoms a person experiences, the more likely they are to have opioid use disorder. ⦁ Mild: 2–3 symptoms present ⦁ Moderate: 4–5 symptoms present ⦁ Severe: 6 or more symptoms present