Opioids Worsen Pain Over Long Term, Study Finds

Opioid-based painkillers could actually make pain worse in the long run, according to a new study performed on mice. 

Researchers found that a short course of morphine after nerve injury “paradoxically and remarkably” doubles the duration of neuropathic pain for months after treatment has been stopped. 

This is the first time such an effect of opioids on neuropathic pain has been observed. 

Over reliance on opioids

Opioids are mainly prescribed for pain relief, particularly in the UK and the USA, which prescribe 77% of the world’s available morphine.

While there has been a recent push in the UK to make opioid prescription a last resort, in the last year alone, 50 million prescriptions for opioids were written. This is a 35% increase over 10 years. In that same time, opioid overdoses have increased by 87% to 12,000. 

A study from 2019 found that the UK’s growing opioid use is being driven partly by the amount of prescriptions being given to surgery patients who don’t necessarily need them.

This inappropriate prescribing of opioids may be leading to increased pain and increased opioid use in the long-term.

Mice study

The recent study on mice looked at how opioids affect pain levels following a nerve injury. 

The findings suggest that the long-term consequences of taking the drugs include increased pain for a number of months after opioid use has discontinued.

Citing the “two-hit hypothesis of microglial priming”, researchers theorise that the injury plus the opioid delivered a kind of ‘one-two punch’ to cells in the spinal cord, leading to exaggerated reactivity.

Lead author of the study, Professor Peter Grace, said: “We found the treatment was contributing to the problem.

“We are showing for the first time that even a brief exposure to opioids can have long-term negative effects on pain.”

Professor Linda Watkins, added: “The implications for people taking opioids like morphine, oxycodone and methadone are great, since we show the short-term decision to take such opioids can have devastating consequences of making pain worse and longer lasting.

“This is a very ugly side to opioids that had not been recognized before.”

Addictive potential  

Increased pain is not the only risk from opioids, they can also be highly addictive.

In fact, a recent study found that people given opioids for pain relief are 25 percent more likely to use the drugs chronically. 

Study author Dr Susan Calcaterra said: “These drugs are highly effective for pain control, but also cause feelings of euphoria.

“For these reasons, patients may ask their physicians for additional opioid medication even after their acute issue is resolved.”

Cannabis over opioids? 

With western healthcare systems largely relying on opioid-based pain medications, could cannabis offer a safer solution?

Well, cannabis is clearly safer, as death from overdose is effectively impossible. The side-effects of cannabis are also much less severe than opioids. 

But when it comes to pain relief, is cannabis as effective as opioids?

There is evidence that CBD and THC target some of the pain pathways in our nervous system to reduce the sensation of pain. A  number of studies also suggest that  cannabis-based medicines are effective for treating chronic pain.

Observational research has also found that the availability of cannabis is associated with reductions in opioid use. 


While opioids are effective at relieving pain in the short term, a new study has found that they can actually increase pain over the long term. 

This finding further highlights how our modern reliance on opioids comes with unintended negative consequences. 

One alternative to opioids could be cannabis, which clearly has a much better safety profile. 

What do you think? 

3 Comments on “Opioids Worsen Pain Over Long Term, Study Finds”

  1. I was speaking to an A&E consultant about this issue and they said to me ‘no-one ever comes into A&E screaming out for cannabis but offer them morphine or oxycodone and they’ll bite your hand off’. It’s a fair point but as the same time it completely misses the point about what the respective purpose of these medications.

    Opioids should only be be prescribed for severe, acute pain, which is what this consultant was seeing in their department daily – injuries and trauma resulting from accidents and emergencies – while cannabis is more appropriate for moderate or chronic pain, so while the consultant made a good argument for the patients they were seeing there is a more nuanced debate to be had and the either/or argument rather misses the point. It’s not (or shouldn’t be) one or the other, severe pain might need opioid medication to bring it under control while moderate pain may be more responsive to cannabis.

    These aren’t hard and fast rules of course but as a chronic pain patient who experiences acute episodes I find cannabis effective for the former and opiates effective for the latter. I don’t think cannabis will ever completely replace opioids as the go-to medication for patents in severe, acute pain but hopefully it is another part of the toolkit for patients experiencing moderate pain.

    For those patents who might otherwise have been prescribed opioids for moderate pain to which they went on to become addicted, or experienced some of the other unpleasant side effects like lethargy, loss of concentration, constipation, emotional disregulation etc, medical cannabis could be a game-changer. For me it’s enabled me to to substitute cannabis for daily opioid medication and and only use opioids for acute episodes. So while I might not be opioid-free, I’m definitely using less and and my tolerance and physical dependence on opioid medication has dropped right off.

    There are side effects to medical cannabis as well of course – recently I went to a comedy gig at a huge venue and really didn’t want to feel stoned in a huge crowd of people, which is something I’ve done before and find really unpleasant, so I had to use opioid medication on that occasion when – for my pain levels at the time – cannabis would have worked just fine. But that’s just another argument for why it’s good to have more than one option to stop pain ruling your life.

  2. While I agree with this article, I disagree there’s only one answer, no opiates.

    They STILL do help for chronic pain patients, if taken properly, and that means the chronic pain patients must understand the medication is only to help and especially with breakthrough pain. Either way, no pain reliever is going to give you full pain relief permanently. Your body will compensate eventually, even in a hospital setting under heavy doses.

    That’s why it’s about education, training and proper prescribing, not taking them away. Mix them up, make sure the patient doesn’t get stuck to one, say every month give a different mixture, a different medicine, compile a list of what works, and rotate it monthly. Ensuring you get care when you need it, and otherwise you’re going to get hyperalgesia, and you’re body’s going to feel pain more intensely, because you’ve been numbing it too much.

    15 years of this for me, and I still haven’t changed dosage normalcy, I sit around 10-15mg standard when needed. 5mg-10mg more for extreme pain. (20mg max of say a regular hydro, or perc.) either way I think you get the point.

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