Why The Brain Loves Opioids

Societies have long coveted opioids for both the euphoria and the pain relief they provide. When chemists extracted morphine from opium poppies, it quickly became the go-to treatment during the American Civil War. After morphine caused widespread addiction, drug companies invented what they thought was a “non-addictive” substitute: a cough syrup called heroin. That turned out poorly for the 20th century.  Today, prescription opioids, like fentanyl and oxycodone, crowd America’s medicine cabinets and its streets.

Opioid overdoses now kill more Americans every year than car accidents. To understand how we arrived here, you’ll need to venture deep into the mind. Here’s why our brains love opioids: when opioids enter the brain, they land on tiny docking stations at the ends of your nerves called receptors. Typically, the receptors catch chemical messengers, called neurotransmitters, to activate your nerve cells.

Opioid receptors do just the opposite. They stop electric pulses from traveling through your nerve cells, also known as neurons. This dampening is handy with pain relief. Say you have chronic back pain. Your inflamed muscles are constantly sending pain signals to your brain via neurons in your spine. Opioids quiet those nerves, relieving your pain.

Opioids have three major receptors: Mu, Kappa and Delta but the Mu receptor is the one to remember. The Mu receptor is responsible for the consequences of almost all opiates. It slows breathing, eliminates pain and fills the mind with warm euphoria. Too much of this opioid off-switch becomes addictive. Opioid addiction starts in the midbrain,where Mu-opioid receptors turn off a batch of nerve cells called GABAergic neurons. GABAergic neurons are themselves an off-switch for pleasure. They prevent other midbrain neurons from flooding the brain’s pleasure circuits with another transmitter, dopamine.

At one stop along these pleasure circuits, the nucleus accumbens, the dopamine triggers a surge of happiness that reinforces the idea that opioid drugs are rewarding. In our brain’s fear center, the amygdala, the dopamine relieves anxiety and stress. It’s just an overall sense of well-being. No problems, just warm. Then, as decision-making brain areas become overwhelmed, cravings set in.

All drugs come with a dark side as they clear the body. This is known as withdrawal. Too much beer causes a hangover the next day. A cocaine high is followed by a crash. But opioids, especially long-lasting ones like methadone, don’t change a person’s outward behaviors. You can still drive and go to work. However, opioids cause brain circuits to slowly adopt a new state of normal. Soon, without opioids in the body, addicts feel constantly anxious and their stress hormones stay elevated.

Opioids typically trigger constipation and tweak body temperature. Remove them, and a person with opioid dependence has persistent diarrhea, hot and cold sweats and goosebumps. Some describe opioid withdrawal as the sickest feeling they’ve ever had and the desperate hunger for relief drives addiction. Here’s the dangerous clause: the potency of opioids diminishes over time if you abuse them.

Eventually, rather than remedy your chronic back problem, your pain becomes linked with the emotional and physical toil of opioid withdrawal. It becomes a vicious cycle. Popping more pain killers or injecting heroin more frequently becomes the way to keep all those bad feelings at bay. If you started recreationally, the struggle against withdrawal becomes all consuming. One may keep chasing that high and you never get original feeling again. You kind of get immune to it, just maintaining and then without it, you’re sick and you need help.