PAIN: Cannabis does not reduce it but makes it more tolerable

 The use of cannabis for medical purposes is now legal in more than 30 states in the United States. Better understanding and characterizing the impact of cannabis and cannabinoids on different pathways of pain reactivity may help explain the belief that cannabis relieves pain and support evidence of efficacy. “But we still have a lot to learn,” concludes this team from Syracuse University in JAMA Psychiatry, which suggests that while cannabinoids do not reduce the intensity of pain, they make it less unpleasant and more tolerable. .

 

This publication coincides with “Pain Awareness Month” and is the first-ever systematic review of experimental research on the effects of cannabis on pain. Cannabinoids are chemical compounds that give the cannabis plant its medicinal and recreational properties. The main author, Martin De Vita, doctoral candidate in clinical psychology, recalls that THC and CBD (cannabidiol) are the main cannabinoids. When ingested, THC binds to receptors in the brain that control pleasure, time perception, and pain. This activity leads to the production of dopamine with an effect of euphoria or relaxation.

 

However, better quality evidence supporting the efficacy of cannabis in the treatment of chronic pain remains to be established. “While patients are convinced that cannabis is effective in relieving pain, its analgesic properties remain poorly understood. explains the lead author, who recalls that so far experimental studies of cannabinoid analgesia in healthy adults have yielded mixed results. It is therefore a very broad review of the literature that is proposed to us, with more than 1,830 experimental studies on cannabis identified, carried out in North America and Europe over a period of 40 years. Then the meta-analysis of the 18 selected studies involving 440 adult participants. The mean study quality and validity score was high and the analyzes did not suggest publication bias. The analysis finds that cannabinoid drugs are associated with:

• modest increases in pain threshold and tolerance,
• but on the other hand to no reduction in the intensity of the “ongoing” pain.

 

Cannabinoids therefore allow a reduction in the unpleasantness of painful stimuli and do not lead to any mechanical reduction in hyperalgesia.

 

An affective rather than sensory effect? Cannabinoid analgesia could thus be linked to an affective component rather than a sensory component. Anyway, as far as THC is concerned. Because studies have mostly focused on THC strains, it's unclear whether other cannabinoids exert different effects on pain.

 

The analysis having been limited to experimental pain, that is to say induced in the laboratory, the team will now continue its research on clinical pain , generally associated with a non-malignant progressive disease and on neuropathic pain , associated with disease or damage to the nervous system, leading to tissue damage.

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BACK PAIN: It leads to disability and death in older women

 Back pain can be very disabling on a daily basis, in the elderly, it can lead to loss of autonomy and death, underlines this study from the Boston Medical Center. Younger people will be embarrassed but struggle to perform daily activities, but older people may want to avoid them for fear of pain or worsening symptoms. This daily incapacity promotes a sedentary lifestyle and isolation, weight gain and the development or progression of various chronic diseases. With a significantly increased risk of premature death, according to these data presented in the Journal of General Internal Medicine.

This study is the first to measure the impact of chronic back pain on mortality. The message from these Boston researchers is clear: half of the effects of persistent back pain in older women is explained by disability and the progressive loss of autonomy in everyday life. Consequences probably similar to those of other joint and muscle pain that can reduce the autonomy and mobility of the elderly patient.  

 

Persistent and frequent back pain is associated with premature death: the demonstration is made on a cohort of 8,321 elderly women, followed on average for 14 years. The researchers assessed the back pain of the participants at inclusion and then 2 years later. During the 4th year of follow-up, participants were asked about common activities of daily living. The analysis reveals that the disability associated with the severity of back pain largely explains the association with mortality. More precisely,

• difficulty performing one or more basic daily activities, such as walking short distances or preparing a meal, explains almost half (47%) of the effects of chronic low back pain on mortality;
• slow performance on more objective measures, such as observed walking speed or repetitive "lifting" of a chair, still explains around a quarter of this association (27% and 24%, respectively);
• of all participants, 56% died after a median follow-up of 14.1 years. A higher proportion of women with persistent and frequent back pain died (65.8%) vs participants without back pain (53.5%).
• After accounting for possible confounders, in these older women, persistent and frequent back pain is associated with a 24% increased risk of death vs no back pain.

 

 

Disability and incapacity explain the majority of the effects of chronic back pain on the risk of death in the elderly patient. Back pain is the leading cause of disability worldwide and women between the ages of 40 and 80 have the highest prevalence of back pain. In epidemiological studies, women report more frequent and severe back pain than men. The study is the first to show a link between the degree of disability related to back pain and mortality.

 

Could better management of back pain prevent disability , improve quality of life and prolong life? Lead author Dr. Eric Roseen raises the question. Studies of the long-term impact of back pain treatments and low back pain self-care strategies need to be conducted.

But already there is a call for clinicians to systematically assess the physical function of older people with back pain and guideline-based back pain management through minimally invasive treatments.

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PAIN: Can it be a self-fulfilling prophecy?

 Yes, pain can be "a self-fulfilling prophecy." We think about it and the pain comes. This brain imaging research, conducted by neuroscientists at the University of Colorado at Boulder, shows that when we expect pain, even if the stimulus isn't painful, we experience pain. The study, presented in the journal Nature Human Behavior, also shows that these misguided prophecies can persist, and with them the associated pain, even when reality repeatedly shows otherwise.

 

Thus, our expectations regarding the intensity of pain can be self-fulfilling: the study even shows via MRI a positive feedback loop between these expectations and perceived pain. Lead author Dr. Tor Wager, a professor of psychology and neuroscience at the University of Colorado sums it up this way: “The more pain you expect to experience, the more your brain responds to pain. The more your brain reacts to pain, the more you expect from it.”

 

The hypothesis of a self-fulfilling prophecy regarding pain has “worked” neuroscientists for decades. While multiple studies have already suggested that our expectations can influence our health, including, for example, our response to treatment, this new research is the first to directly model this feedback loop dynamic between our expectations and the pain experienced, and to decipher the underlying neural mechanisms.

The study is conducted here with 34 subjects, who learned to associate a symbol with a low temperature and another symbol with an intense and painful heat. The subjects then had functional magnetic resonance imaging (fMRI), which measures blood flow in the brain, a hallmark of neural activity. For 60 minutes, participants were presented with low or high pain indices and then asked to rate the level of pain expected. Finally, they underwent the application of different degrees of painful heat to the forearm or leg, the highest temperature corresponding "to that of a cup of hot coffee". The study shows that:

• when the subjects expect a high and therefore more painful temperature, the brain regions involved in fear and threat are activated during this expectation;
• the areas involved in the generation of pain are activated in turn;
• suggesting that expectations had a rather profound effect, influencing how the brain processes pain.
• expectations also seem to strongly influence the ability of subjects to learn from their experiences; thus many subjects have a high "bias" despite their previous experiences. High expectations thus seem to reduce the ability to learn – with regard to the sensation of pain.

 

 

Implications for recovery from painful conditions? These results suggest that expectations about pain and even treatment outcomes may, in some situations, influence optimal recovery. Positive expectations could indeed have the opposite effect, a reduction in perceived pain and faster recovery.

 

Finally, the research may help explain why, in some patients, chronic pain may persist long after the damaged tissue has healed.

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