The use of cannabis to relieve pain is controversial, not just for legal reasons but also because of the conflicting research findings with regards to its efficacy. A recent study by Martin De Vita et al., from Syracuse University in New York, looked into the effects of cannabis on pain. They selected, reviewed and analysed studies that had researched the effect of cannabis on experimentally induced pain. De Vita et al. conclude that “although the cannabinoids examined in this review may prevent the onset of laboratory-induced pain by increasing pain thresholds, they do not appear to reduce the intensity of experimental pain that is already being experienced. Instead, these substances make experimental pain feel less unpleasant and more tolerable, suggesting a notable influence on affective processes. The cumulative research synthesized in this review has helped characterize how cannabis and cannabinoids affect different dimensions of pain reactivity.”
There are 2 components to pain: the purely sensory component and the affective (emotional) component. It’s been known for a while that opioids and our endogenous opioid pathways play an important role in sensory pain perception. It now appears that cannabis and our endogenous cannabinoid pathways play a part in the emotional dimension of pain. Interestingly, mindfulness meditation, which has proven effects on pain relief, doesn’t use opioid pathways. In fact, the mechanisms underlying mindfulness meditation’s pain-relieving effects are as yet unknown. Could it be possible that they employ cannabinoid receptors and pathways?
Yu et al recently published the results their study on the effects of acceptance and commitment therapy (ACT) in people with chronic pain. The article appeared in last month’s issue of Journal of Pain. ACT “is an empirically-based psychological intervention that uses acceptance and mindfulness strategies mixed in different ways with commitment and behavior-change strategies, to increase psychological flexibility. The objective of ACT is not elimination of difficult feelings; rather, it is to be present with what life brings us and to “move toward valued behavior”. Acceptance and commitment therapy invites people to open up to unpleasant feelings, and learn not to overreact to them, and not avoiding situations where they are invoked” (Wikipedia).
The study involved over 400 hundred adults referred to a pain management clinic. Treatment significantly improved pain acceptance, pain-related interference, work and social adjustment and depression. This was true immediately post-treatment as well as at a 9-month follow-up. ACT also changed something known as “self-as-context” (SAC). SAC can be described as “the you that is always there observing and experiencing and yet distinct from one’s thoughts, feelings, sensations, and memories” (Wikipedia). Of note was the fact that positive changes in “self-as-context” were associated with positive changes in outcomes.
It’s really interesting how acceptance and commitment therapy has incorporated Buddhist principles and techniques such as mindfulness, acceptance and the self. In fact, it seems that the use of Buddhist philosophy and principles are becoming more common within therapy nowadays.
A study by Whitlock et al from the University of California, published in this month’s Jama Internal Medicine, looked into the relationship between persistent pain, memory decline and dementia. Over 10,000 senior citizens (median age of 73 years) from the Health and Retirement Study were followed for 12 years.
At baseline, persistent pain affected 11% of participants and was linked with more restrictions in daily activities and more symptoms of depression. Those with persistent pain had a greater risk (9%) of having a more rapid memory decline than those without pain. They also had a smaller increase in risk (2%) of developing dementia. These changes significantly increased the chances of being unable to manage medications (16%) or finances (12%).
What’s the causal connection between chronic pain, memory decline and dementia? The authors believe the severity of pain can decrease attention capacity and impair memory consolidation. Additionally, pain leads to stress, and stress has been shown to promote cognitive decline, mainly through hypotrophy of the hippocampus. In my opinion, the disruption of sleep can also contribute to poor memory and a decline in cognitive ability because, as we know, sleep is involved in memory processing and consolidation.
Fortunately, physiotherapy, rehabilitation, relaxation and mindfulness meditation are effective at addressing chronic pain.
Earlier this year Billington et al. from the University of Liverpool published the results of their study looking at the effects of shared reading (SR) on people with chronic pain. The shared reading model they used was the one employed by the charity “The Reader“. “The Reader is an award-winning charitable social enterprise working to connect people with great literature through shared reading. We’re here to bring books to life, creating welcoming environments in which personal feeling is recognised and valued, forming vital connections between people and literature through which everyone can feel more alive.”
The researchers concluded “Qualitative evidence indicates SR’s potential as an alternative or long-term follow-up or adjunct to CBT in bringing into conscious awareness areas of emotional pain otherwise passively suffered by patients with chronic pain. In addition, quantitative analysis, albeit of limited pilot data, indicated possible improvements in mood/pain for up to 2?days following SR. Both findings lay the basis for future research involving a larger sample size.”
The preliminary findings are encouraging. There may be other factors such as distraction, social bonding and the benefits of having regular scheduled activities that may also play a part in improving the well-being of the participants.
“When touched with a feeling of pain, the uninstructed run-of-the-mill person sorrows, grieves, and laments, beats his breast, becomes distraught. So he feels two pains, physical and mental. Just as if they were to shoot a man with an arrow and, right afterward, were to shoot him with another one, so that he would feel the pains of two arrows.”
Renaud Massart et al from McGill University have recently published an article in Scientific Reports on the effects of chronic pain on the body. “Chronic pain” is pain that has lasted for 6 months or more. The study was performed on rats with induced nerve injuries.
The results showed epigenetic changes in the DNA of the prefrontal cortex and in the DNA of T cells. Their findings support the notion that persistent pain affects multiple biological systems. It’s possible that future research will show changes to other systems as well.
Statins are widely used to lower cholesterol and reduce the risk of cardiovascular disease. Like a lot of drugs, statins come with some side effects. Myopathy, in the form of muscle weakness, pain and cramps is one of the most important adverse effects. A group of researchers from Radboud University Medical Center in the Netherlands may have found out why statins can sometimes cause muscle problems. Their findings are published in this month’s issue of Cell Metabolism.
They found that statins can significantly inhibit mitochondrial (complex III) activity. This effect is primarily from statin lactones rather than the acid forms. These findings could lead to new classes of cholesterol-lowering drugs without the unwanted muscle effects.
Most of us have us have used paracetamol at some point in our lives, whether to bring down a fever, for a headache, joint pain or some other painful condition. In fact, if we have a look in our medicine cabinets we’ll probably find a box…or two! Machado et al. from George Institute for Global Health at the University of Sydney recently reviewed the scientific literature with the aim of investigating the efficacy and safety of paracetamol (acetaminophen) in the management of spinal pain and osteoarthritis of the hip or knee. They included 13 randomised controlled trials in their review and the results were published in the BMJ.
They found that for low back pain, paracetamol was ineffective at reducing pain or disability and at improving quality of life. It’s important to point out that by “ineffective”, they mean that paracetamol did not provide more benefit than a placebo. For hip and knee osteoarthritis they found that there was a significant, although not clinically important, effect on pain and disability in the short term. Adverse events were not more likely with paracetamol than placebo but patients taking paracetamol are 4 times more likely to have abnormal results on liver function tests.
Although the clinical importance of the last finding is uncertain, paracetamol has been linked to increasing incidence of mortality, increased risk of cardiovascular, gastrointestinal and renal disease. This study has prompted the BMJ to release an editorial discussing the use of paracetamol for back pain and osteoarthritis. One of the problems for GPs is that the National Institute for Clinical Excellence (NICE) recommends paracetamol as the first port of call for low back pain and arthritis. Taking this option away leaves NSAIDS and opioids which both present even more health risks… Non-pharmalogical options should be pursued and developed i.e. physical activity and exercise, weight loss, nutritional supplements and physiotherapy of course!
Neuropathic pain is a chronic pain condition caused by a damaged or dysfunctional nervous system. It is characterised by shooting and burning pain that lasts long after the initial onset. Common causes of neuropathic pain include:
- back, leg and hip problems
- facial nerve problems
- HIV or AIDS
- multiple sclerosis
- spine surgery
Unfortunately neuropathic pain doesn’t respond much to conventional analgesics but instead, antidepressants (amitriptyline and duloxetine) and anticonvulsants (gabapentin and pregabalin) have been found to help relieve pain.
A new study published in this month’s edition of Neuron by Thomas Nevian et al from the Department of Physiology at the University of Bern has revealed some of the mechanisms involved in neuropathic pain. In a mouse model, they found that neurons in the gyrus cinguli, a part of the brain found in the limbic system (usually associated with emotion) are modified by pain forming a “pain memory”. Neurons in the gyrus cinguli become more excitable due to a down-regulated ion channel. This leads to an increased number of nerve impulses which the brain perceives as pain.
The researchers managed to restore the function of the ion channel by activating a receptor sensitive to serotonin. This explains the success of some antidepressants in treating neuropathic pain. Nevian et al were able to identify the specific subtype of serotonin receptor that was more efficient at reducing the perception of pain. Excitingly, this could lead to the development of more effective drugs to treat neuropathic pain.
A group of German researchers recently published the results of a study looking into the benefits of meditation on people with chronic neck pain. The article was published in The Journal of Pain. They studied about 90 people who had neck pain for an average of 11 years. The average age of the participants was 50 years. Their results found significant improvements in pain reduction and pain coping but no effect on functional disability.
The findings suggest that meditation could be used as an adjunct alongside physical treatments that provide functional benefits.