Table 1.

Relevant studies showing the association of depression and rheumatoid arthritis

Author/publication year	Country	Study design	Population	Sample size	Major findings
1. Rahim et al. [57]	Malaysia	Cross-sectional study	RA patients	192	Depression in RA increases the risk of suicidal ideation
2. Vallerand et al. [58]	Canada	Retrospective cohort study	403,932 MDD and 5,339,399 without MDD	5,743,331	Molecular mechanism for link between depression and inflammation
3. Marrie et al. [59]	Canada	Retrospective cohort study	19,572 IMID including 6,119 IBD, 3514 MS, 10,206 RA, 97,727 age-, sex- and geographically matched HC	117,299	Inflammation and immune dysregulation is partly responsible for depression, anxiety, and bipolar disorder
4. Marrie et al. [60]	Canada	Case–control study	28,384 IMID cases (IBD: 8695; MS: 5496; RA: 14,503) and 141,672 matched HC	170,056	Suicide risk was significantly increased in patients with RA, even after adjusting for other causes
5. Gafvels et al. [61]	Sweden	Prospective study	89 DM, 100 RA	189	Treatment of depression in patients with RA improves mental and physical health
6. Demmelmaier et al. [62]	Sweden, USA	Cross-sectional study	Low/moderate fatigue (n = 174) severe fatigue (n = 95)	269	Physical activity improves mental health and fatigue
7. Wang S-L et al. [63]	Taiwan	Retrospective cohort study	3657 RA and 14,628 controls	18,285	In patients with RA, there is a significant association between depression and an increased level of pain