Why an Opiate's Impact on the Brain Can Cause Addiction

Five pills of OXYCOCONE.
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Opiates, sometimes known as narcotics, are a type of drug that act as depressants on the central nervous system (CNS). Opiates come from opium, which can be produced naturally from poppy plants; opioids are chemically synthesized opiate-like drugs.

Some of the most common opiates and opioids include:

  • Morphine (Kadian, Avinza)
  • Codeine
  • Hydrocodone (Vicodin)
  • Fentanyl
  • Oxycodone (OxyContin, Percocet)
  • Heroin

Opiate Use and Abuse

Opiate and opioid use is on the rise globally, so it may come as no surprise that abuse and addiction to such substances have also increased in recent years, peaking in 2012 and dropping slowly since then. According to the National Institute on Drug Abuse:

  • In 2018, opiate painkillers were prescribed more than 168 million times.
  • Between 26 and 36 million people worldwide abuse opiates.
  • Over two million adults in the United States suffer from substance abuse problems related to the abuse of opiate painkillers.
  • Nearly half a million U.S. adults are addicted to heroin.
  • In 2010, the overuse of opiate painkillers resulted in nearly 17,000 deaths in the United States.
  • About 75% of all people with an opioid addiction disorder end up switching to heroin as a cheaper source of opioids.

How Opiates Affect the Brain

Both humans and animals have opiate receptors in the brain. These receptors act as action sites for different types of opiates, such as heroin and morphine.

The reason the brain has these receptor sites is because of the existence of endogenous (internal) neurotransmitters that act on these receptor sites and produce responses in the body that are similar to those of opiate drugs.

Opiates and opioids work by binding to specific receptors in the brain, mimicking the effects of pain-relieving chemicals that are produced naturally. These drugs bind to opiate receptors in the brain, spinal cord, and other locations in the body. This blocks the perception of pain. Opiates can cause feelings of well-being, but they can also cause side effects such as nausea, confusion, and drowsiness.

In addition to relieving pain, opiates can lead to feelings of euphoria. While these drugs are often very effective in treating pain, people can eventually develop a tolerance, so they require higher doses to achieve the same effects.

As the effects of opiate drugs become more tolerated, people may begin taking increasingly higher doses to experience the same pain-relieving effects and to reduce symptoms of withdrawal. Symptoms of opiate withdrawal can include anxiety, muscle aches, irritability, insomnia, runny nose, nausea, vomiting, and abdominal cramping.

What makes prescription opiates so potentially dangerous? They affect powerful reward systems in the brain. Some people can even become addicted when taking them exactly as prescribed, but the dangers can be increased by not taking them as directed or by combining them with other substances including alcohol and other drugs. Also, there are individual differences in genetic vulnerability to opiate addiction.

An estimated 50 million adults in the U.S. suffer from some type of chronic pain. Opioid pain relievers are often prescribed to treat injury-related pain, dental pain, and back pain. When taken as directed, they are generally not likely to lead to overuse or addiction. People who use opiates to control pain should contact their healthcare provider if they believe they may be developing a tolerance or addiction.

If you or a loved one are struggling with substance use or addiction, contact the Substance Abuse and Mental Health Services Administration (SAMHSA) National Helpline at 1-800-662-4357 for information on support and treatment facilities in your area.

For more mental health resources, see our National Helpline Database.

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5 Sources
Verywell Mind uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. National Institute on Drug Abuse. Opioids.

  2. Centers for Disease Control and Prevention. U.S. opioid prescribing rate maps. Updated March 5, 2020.

  3. National Institute on Drug Abuse. Prescription opioid use is a risk factor for heroin use. Updated January 2018.

  4. Shah M, Huecker MR. Opioid withdrawal. In: StatPearls [Internet]. StatPearls Publishing; updated June 4, 2019.

  5. Dahlhamer J, Lucas J, Zelaya, C, et al. Prevalence of chronic pain and high-impact chronic pain among adults — United States, 2016. MMWR Morb Mortal Wkly Rep 2018;67:1001-1006. doi:10.15585/mmwr.mm6736a2

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