LAUSR

Abstract Background Various cytokine changes have been reported in patients with different types of depression. However, it is unclear whether depression is a consequence of brain general response to chronic or severe immune inflammation, or specific cytokine changes contribute to a different subtype of depression. Methods Two terms (cytokine OR inflammation) AND (subtype of depression) from Pubmed were used to select the patients with first-episode or drug-free. A total of 39 articles in 7 subtypes of depression were selected and included in the review. Results M1 and T helper (Th) 1 pattern dominates in major depression, such as increased interleukin (IL)-1β, IL-6, tumor necrosis factor (TNF)-α and interferon (IFN)-γ, but reduced IL-10. Similarly, M1 cytokines IL-1β, IL-6 and TNF-α are increased except for transforming growth factor in bipolar disorder, and IL-1β, IL-6, TNF-α and IFN-γ increased in seasonal affective disorder. However, a certain cytokine change is correlated to a subtype of depression. For example, pro-inflammatory cytokines are altered during different period of prenatal and postpartum depression. Th phenotypes difference between atypical depression and melancholic depression is related to IL-2 and IL-4. As well, higher levels of IL-6 and lower IL-2 in suicide attempters compared to non-suicidal, etc. Limitations Studies in specific depression were not enough. Inconsistent investigation designs and results were reported in different subtypes of depression. Conclusions A certain immune/cytokine pattern may be related to a subtype of depression. However, Big Data Analysis and Precision Medicine should be utilized to figure out the real connection between cytokine changes and depression.