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The Science Of Opioid Dependence

It’s not an understatement to say America is coping with an entire generation’s worth of people suffering  from opioid dependence. And to top it all off, there’s plenty of blame to go around.

How The Brain Gets “Hijacked”

Opioid addiction starts in the midbrain. Prescription painkillers, heroin, morphine, virtually any kind of opiate neutralize GABAergic neurons. These neurons are responsible for holding back the flood of dopamine, a natural, and pleasure inducing neurotransmitter.

  • Media reporting can misrepresent how opioids “hijack” the brain’s chemistry, causing addiction.

Surges of dopamine to pleasure circuits in the forebrain create a sense of warm, peaceful euphoria. Almost simultaneously, dopamine hits the amygdala – a small almond shaped mass of gray matter responsible for how people regulate fear and emotion – causing any stress, anxiety or tension to evaporate.

The amygdala and the area in the forebrain – nucleus accumbens – communicate with the prefrontal cortex, where human decision-making processes occur. The sense of euphoria convinces the circuits in the prefrontal cortex that these “feelings and sensations” are good.

In other words, these two events chemically condition the brain to view, accept and crave the “reward” opiates bring on. The brain is now trapped in a cycle where seeking out an opiate “reward” or “high” is the main focus.

The Blame Game

The opioid epidemic continues to worsen, so who’s to blame? According to the Centers for Disease Control and Prevention’s (CDC) provisional count, around 65,000 people died from drug overdoses in 2016, largely because of fentanyl-laced heroin and prescription painkillers.

  1. Physicians accuse pharmaceutical companies for claiming prescription painkillers weren’t addictive.
  2. Public health officials decry physicians for writing too many opioid prescriptions.
  3. Meanwhile, law enforcement is unable to stop heroin and deadly synthetic opioids, like fentanyl, from getting into the country illegally.

A Vicious Cycle

Though some individuals are able to use heroin or prescription painkillers non-medically for a short period of time and still function, opioids are particularly pernicious where another element of addiction is concerned – tolerance.

The longer a person uses opiates, the more dependent the mind and body are on the drug, and the more they need to feel its soothing effects. This is really when the “rewards” of opiate addiction turn on users and become an incredibly painful, both physically and mentally.

Anyone can develop an addiction to opioids and heroin. There are, though, some populations of people that are more susceptible, like those coping with chronic pain.

A pain and addiction researcher at UCLA, Cathy Cahill believes that big mood swings brought on by withdrawal are, likely, what contribute to drug seeking behavior even when the consequences of addiction have gotten desperate.

  • So around and around they go using, withdrawing and then using again to relieve the painful symptoms of withdrawal.

“The basic view is some people start with the pain trigger [the chronic back problem, for example], but it gets partially substituted with the negative reinforcement of the opioid withdrawal,” Cahill told PBS News Hour.

  • Another study, done in 2012, found patients with mood disorders, such as depression, anxiety and bipolar disorder among others, are more likely to abuse opioid medications.

The Withdrawal Process

Heroin and opioid withdrawal is not fatal, though a person experiencing the symptoms will certainly feel as if they might die. Most fatalities from opioids are a result of relapse. After a period of sobriety, when a person’s tolerance returns to normal, using the same amount of they used before stopping is deadly. More heroin or prescription painkillers than a person’s body has tolerance for will slow their respiratory system to the point that they stop breathing altogether.

When the brain’s not receiving any opiates, or not enough because of a person’s tolerance, GABAergic neurons are still constantly firing electric pulses the drug conditioned it to transmit. The result is no longer a “high,” that sense of warm, peaceful euphoria. Now, the amygdala and the forebrain, essentially, go into panic mode and cause symptoms of withdrawal include:

  • Anxiety and depression
  • Diarrhea, nausea, vomiting, abdominal cramping
  • High blood pressure and rapid heartbeat
  • Insomnia
  • Muscle aches and restlessness

Treatment and Recovery

Treatment for opioid addiction ranges from 12-step programs to medically assisted therapies (MAT), which replace opioids like heroin with other, less powerful, opioid medications – methadone or buprenorphine. It should be noted, however, that MAT only works in about 60 percent of patients.

According to the PBS News Hour piece, replacement therapies, like methadone and buprenorphine, don’t work at all with synthetic opioids as powerful as fentanyl, which is responsible for a massive number of fatal overdoses in the United States.

Scientists continue to research and record the effects opioid addiction has on the human brain. The consensus for now is that there’s no easy medical fix for the soaring rate of opioid addiction in the country.


Short Video – Why the Human Brain Loves Opioids



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