What are the cause(s) of fibromyalgia?

Question

Looking at The American College of Rheumatology 1990 criteria for the classification of fibromyalgia (Wolfe, et al. 1990), they indicate that this was first indentified in the late 1970s.

The seminal 1977 paper by Smythe and Moldofsky, “Two contributions to understanding of the ‘fibrositis’ syndrome”, revived interest in the long known but generally neglected syndrome of fibromyalgia (fibrositis). By proposing diagnostic criteria, the authors stimulated other investigators and began a cascade of interest that would lead to the publication of more than 60 research papers and to increasing clinical acceptance of the syndrome.

they also point out that according to some investigators:

fibromyalgia may be thought of as a psychological disorder or, perhaps, a local myofaseial pain syndrome

Wolfe et al. (1990) proposed a set of criteria for diagnosing fibromyalgia which was widespread pain in combination with tenderness at 11 or more of 18 specific tender point sites.

Websites I have visited state that the cause(s) of fibromyalgia are unknown, but seeing as it was starting to be accepted as a real problem in 1977, this has had 42 years for study.

If there is no known cause, I am wondering what the latest consensus is regarding possible causes.

References

Wolfe, F., Smythe, H. A., Yunus, M. B., Bennett, R. M., Bombardier, C., Goldenberg, D. L., ... & Fam, A. G. (1990). The American College of Rheumatology 1990 criteria for the classification of fibromyalgia. Arthritis & Rheumatism: Official Journal of the American College of Rheumatology, 33(2), 160-172. doi: 10.1002/art.1780330203

Answer 1

I have had a pain management course a couple of years ago - this was my research topic. As you pointed out the reasons are still unknown, also the treatment is basically aimed at treating symptoms an managing life with pain. This might be interesting to read if you are interested in this procedure called multimodal pain therapy [1] The tender points are still the way of diagnosing FM.

The best english Version I found is so far about FM is the NHS website [2] who have lined up all suspected contributing factors quite nicely (and was just recently updated):

Abnormal pain messages -For unknown reason the receptors react differently to pain and the threshold of identifying pain and "just" normal sensations is going down

Chemical imbalance -Serotonin, noradrenaline and dopamine are unusual low in fibromyalgia patients - please note, especially this is not something that can be assumed safely as a cause, it could very well also be a result from being constantly in pain.

Sleep problems -That originally was assumed as a result of Fibromyalgia, but today we also see it as a possible risk factor. As mentioned above a clear cause and effect connection is not easy to establish

Genetics -Some genetic prevalence is found, but since FM is very seldom, that also is not easy to prove.

Trigger - As you mentioned psychical stress is one of the things that is quoted, but also Injuries, infections, surgery and even giving birth.

I myself have seen around 10 FM patients, in my very limited personal experience most of them were post Injury/Surgery, some post viral infection and one was completely without any of the expected triggers and "just" had a depression The studies often point also at other risk factors like smoking, unfortunately the same thing applies as before, due to small numbers and retrospective studies cause and effect are not clearly separable.

[1] https://www.americannursetoday.com/multimodal-multidisciplinary-therapy-pain-management/ [2]https://www.nhs.uk/conditions/fibromyalgia/causes/