A large study has found that there is not enough evidence to suggest antidepressants are effective at treating chronic pain. Despite some prior evidence suggesting that antidepressants do help reduce neuropathic pain, there has never been a large meta-analysis of the papers, and now the results do not appear to be as clear.
Experts urge caution when reading into the data, however, and suggest sticking to antidepressants if they are working for you.
Chronic pain is described as pain that continues for longer than 12 weeks despite medicine or treatment. The true underlying mechanisms are unclear and there are many ways it can arise, but the systems that cause chronic pain are thought to directly overlap with those involved with depression. This is why antidepressants were thought to be effective at treating the pain, as they directly target the neurotransmitter pathways thought to be the culprit.
To understand whether they are actually effective, researchers from the UK scoured databases looking for any study or clinical trial where people with chronic pain were treated with antidepressants. They then performed a network meta-analysis on the data to rank all the antidepressants used from best to worst.
In total, 176 studies were found encompassing almost 29,000 people, who were treated with a total of 89 different drugs and combinations of treatments. The pain was mainly a result of fibromyalgia, nerve pain, or musculoskeletal pain, and the treatments were most often SNRIs, TCAs, and SSRIs.
The results showed that one antidepressant, called duloxetine, may help treat pain, with patients taking a standard dose feeling better than when they took a placebo more often than not. Another drug may help, called milnacipran, but there was not enough data to say for certain.
That’s where the good news ends, however. For the rest of the drugs, the researchers could not find enough evidence to suggest they have any effect on pain and were not confident in reaching a conclusion for any of them. Some appeared to have a minor effect on mood, but the studies did not take into account mental health conditions, so the researchers were not confident in the results.
The data did not provide reliable evidence for the safety of antidepressants as a treatment for chronic pain in either the short or long term.
The team hopes the data can be used to influence policy in prescribing antidepressants for each individual person. Experts suggest that the results might not state that the drugs do not work, but instead highlight the need for higher-quality clinical trials and an individual-centered approach.
“What this comprehensive analysis demonstrates is that when clinical trials are designed poorly under the assumption that everyone’s experience of pain is uniform, most antidepressants appear to have limited use for treating chronic pain,” Dr Ryan Patel, Prof Anthony Mellows/King’s Prize Fellow at King’s College London, who was not involved in the study, said in a statement.
“Even when the cause of chronic pain is the same, the biological changes that occur in the nervous system are varied and so it is no surprise that pain presents differently from person to person, and not everyone will respond to the same drugs. In most areas of medicine the aim is to match the treatment selection to the underlying biology. The question that should be asked is not ‘are antidepressant drugs effective for treating pain?’ but ‘for whom are antidepressants effective?’"
The review can be found at Cochrane Reviews.