Table 1. Summary of included studies showing the prevalence of depression in patients with FM.

MDD: major depressive disorder; FM: fibromyalgia.

References	Design	Sample size	Population	Conclusion
Kleykamp et al. 2020 [49]	Meta-analysis	-	80% of patients were females.	The most prevalent comorbidity in FM is depression (not specified) and MDD.
Loge-Hagen et al. 2019 [50]	Meta-analysis	1,316	FM as the primary diagnosis, no other rheumatologic disease, 18 years old or more.	One-fourth of all patients diagnosed with FM presented with MDD, and more than half of them experienced MDD throughout their lives.
Singh and Kaul 2018 [51]	Cross-sectional	Cases: 80 patients with FM. Controls: 72 healthy individuals.	Groups were matched by sex and age, no current treatment with an antidepressant, no comorbidities.	Higher prevalence of depression (72.5%) in patients with diagnosed FM in comparison to the control group.
Kassam and Patten 2006 [52]	Population-based cross-sectional	115,160	Previously diagnosed with FM, 18 years old and older.	The annual prevalence of MDD was three times higher in FM patients. Prevalence remained high in all the groups.