Table 3. Summary of studies exploring the prevalence and treatment of chronic pain-induced depression.

SNRIs: serotonin-norepinephrine reuptake inhibitors; BrdU: bromodeoxyuridine; CBT: cognitive behavioral therapy; MDD: major depressive disorder; HDAC: histone deacetylase; VAS: visual analog scale

Reference	Study Type	Population	Conclusion
Alhalal et al. (2021) [19]	Cross-sectional study	233 chronic pain patients	Pain disability showed a significant prediction of depression, 36% of the patients had depression
Ma et al. (2021) [18]	Cross-sectional study	15,213 individuals from the 2015 China Health and Retirement Longitudinal Study	Increased severity of pain increased the likelihood of the individuals developing depression
Ferreira et al. (2020) [34]	Systematic review	5318 participants	Moderate evidence that SNRIs decreased back pain in patients
Schäfer et al. (2020) [27]	Narrative review		Physical activity has a positive effect on the prevention of chronic pain
Yalcin and Barrot (2019) [22]	Review	Population of Denmark, United States, and Spain	Elevated frequency of suicidal deaths in patients with fibromyalgia
Duric and McCarson (2019) [13]	Randomized control trial	Rodents	Reduction in BrdU positive cells in rodents after exposure to long periods of stress
Fisher et al. (2017) [37]	Review	27 clinical trials with children and adolescents	Psychotherapy reduced chronic headache in children and adolescents
Cherkin et al. (2017) [36]	Randomized clinical trial	342 patients between 20 and 70 years	Patients given CBT had greater improvement in function
Scherrer et al. (2016) [29]	Cohort study	Three American health systems’ data (Veterans Health database, Baylor Scott and White Health, and the Henry Ford Health System)	18% increase in risk for depression in patients taking opioids for 31-90 days than patients taking opioids for 1-30 days
Descalzi et al. (2015) [3]	Review	Mice	Removal of HDAC5 reduced depression-like behaviors in mice
Dureja et al. (2014) [16]	Epidemiological study	5004 respondents from India	Patients with chronic pain found it difficult to keep an independent lifestyle
Annagür et al. (2014) [23]	SCID-based prospective study	108 pain outpatient clinic patients at the Selcuk University aged 18-56 years	49.1% prevalence of depression in chronic pain patients
Proctor et al. (2013) [24]	Retrospective cross-sectional study	216 chronic pain patients in a neurodiagnostic clinic in the United States	44.4% prevalence of depression in chronic pain patients
Kassam and Patten (2006) [21]	Cross-sectional study	115.160 Canadian adults	Prevalence of MDD in patients with fibromyalgia was almost three times more than in subjects without it
Rowbotham et. Al (2005) [31]	Randomized clinical trial	47 neuropathic pain patients	Pain relief was seen in 53%-80% of the participants
Bair et al. (2003) [7]	Literature Review	Chronic pain patients from various clinics	Increase of lifetime prevalence of depression in chronic pain patients  from 12% to 32% and from 32.4% to 56.8%
Shimodozono et al. (2002) [33]	Open label study	31 patients with central poststroke pain	Significant improvement in the VAS and Zung Self-Rating Depression Scale in the patients