A study of more than 1,100 brain scans has concluded that clinical depression can be categorized into four unique subtypes defined by distinct patterns of abnormal connectivity in the brain. These subtypes are associated with different symptom profiles and probably differ in their response to different treatments.
Drysdale, A. T., Grosenick, L., Downar, J., Dunlop, K., Mansouri, F., Meng, Y., … Liston, C. (2017). Resting-state connectivity biomarkers define neurophysiological subtypes of depression. Nat Med, 23(1), 28–38. Retrieved from http://dx.doi.org/10.1038/nm.4246