The review has been published by The BMJ today.
Their findings are based on analysis of published data from 33 randomised controlled trials involving more than 5,000 adults with low back or neck pain, sciatica, or hip or knee osteoarthritis.
These trials tested six classes of antidepressants:
- serotonin-noradrenaline reuptake inhibitors (SNRIs)
- selective serotonin reuptake inhibitors (SSRIs)
- noradrenaline-dopamine reuptake inhibitors (NDRIs)
- tricyclic antidepressants
- tetracyclic antidepressants
The study set a difference of 10 points on a 0-100 scale for pain as the smallest worthwhile difference between groups, which is a common threshold in studies of chronic pain.
Key findings:
- SNRIs had a trivially small effect on back pain, reducing pain by just 5.3 points out of 100 on the pain scale compared with placebo after three months. This amount is unlikely to be considered clinically important by most patients.
- SNRIs had a slighter stronger effect on osteoarthritis pain after three months, with an average difference of 9.7 points on the pain scale compared with placebo. This amount is still small, but close to the 10 point difference needed for antidepressants to be considered worthwhile by some patients.
- Tricyclic antidepressants were ineffective for back pain and related disability
- Tricyclic antidepressants and SNRIs might reduce pain in people with sciatica (pain down the leg associated with back pain), but the evidence was not certain enough to draw any firm conclusions.
- SNRI antidepressants significantly increased the risk of patients experiencing an adverse event; about two-thirds of patients taking this class of antidepressant had at least one adverse event such as nausea.
Dr Ferreira said this information could help clinicians and patients make more informed decisions about whether to treat chronic back pain and osteoarthritis pain with antidepressants.
The trials were designed differently, and were of varying quality, but the researchers were able to allow for this in their analysis. Most of the data came from industry sponsored trials.
As such, the Researchers say that their review updates the evidence for back pain, sciatica, and osteoarthritis, and could help clinicians and their patients decide whether to take antidepressants for chronic pain.
But they conclude: "Large, definitive randomised trials that are free of industry ties are urgently needed to resolve uncertainties about the efficacy of antidepressants for sciatica and osteoarthritis highlighted by this review."
In a linked editorial, researchers at the University of Warwick call for clearer guidance to inform a consistent approach to use of antidepressants for people with painful disorders.
They acknowledge that some patients might choose to try antidepressants for a small chance of a worthwhile reduction in pain after three months.
Overall, however, they argue that drug treatments "are largely ineffective for back pain and osteoarthritis and have the potential for serious harm. We need to work harder to help people with these disorders to live better with their pain without recourse to the prescription pad."
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