Chronic pain is a highly disabling condition that poses significant therapeutic challenges. Various treatments are available, in most cases with a modest degree of efficacy. A recent study has brought new insights into the management of this condition with injections. As odd as it may seem, the study found that injections below the skin of patients with chronic low back pain, even when known to patients to be placebos, were more effective than usual care, even in the long term. Functional brain imaging (MRI) scans revealed that these injections engaged brain pathways known to reduce pain. Although the effect was modest, it was still comparable to several commonly used treatments that often come with side effects, such as medications.
(Read more about placebo here).
Are injections effective solely as placebos?
The findings of this study prompt a reflection on the use of injections for chronic pain, not necessarily limited to low back pain. Placebo injections demonstrated a long-term impact on pain reduction, which was linked to pain-alleviating brain activities. This raises important questions about the mechanisms behind their effectiveness. One potential explanation is the power of expectation associated with placebos, which may contribute to long-term pain relief.
In addition, in a previous blog, I have discussed other reasons why injections that are expected to have only short-term effect can lead to long-lasting pain relief (read the blog here):
Reduced excitability of pain pathways: A temporary anesthetic block may result in a longer-lasting reduced excitability of pain pathways, ultimately leading to long-term pain relief.
Positive cognitive and emotional processes: Being pain-free for several hours after an anesthetic injection can trigger positive cognitive and emotional processes, resulting in long-term pain relief.
Facilitated mobility: Temporary pain relief can facilitate mobility, which may help reduce pain in the long term.
It is important to note that these explanations are largely speculative due to the very limited mechanistic research on injections.
Implications for chronic pain management
What do the results of the above-mentioned study mean for the management of chronic pain? Should we just give saline injections and hope that patients will improve thanks to a placebo effect? My answer is negative. The study is relevant to improve our understanding of why injections may work. However, telling patients that we are administering a placebo is not applicable to the clinical world. It is also not acceptable to offer treatments of proven inefficacy and rely on a placebo effect.
My suggestion is that injections with minimal risks and a valid pharmacological or pathophysiological basis can be considered acceptable, even in the absence of robust evidence of effectiveness due to limited research. Unfortunately, this may be the best option given the scarcity of high-quality research on injection efficacy, and the frequent lack of alternatives in patients who have tried almost everything and still have a poor quality of life. In a worst-case scenario, injections with uncertain effectiveness may still produce positive outcomes through a placebo effect. Ultimately, what matters is the benefit to patients, with the expectation that forthcoming research will offer a more substantial basis for clinical decision-making.
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