"All that number-crunching yielded four different “biotypes” of depression. They were differentiated from each other (and the control group) at a neural level. Brains whose humans had more depressive anxiety had reduced connectivity in brain networks associated with fear and understanding negative emotional stimuli; people with anhedonia — or difficulty feeling pleasure — had hyperconnectivity in brain areas associated with reward processing and motor control.
The results also sliced fascinatingly across other conditions. The researchers found that while none of the 39 people in the analysis with generalized anxiety disorder met the clinical criteria for depression, a full 69.2 percent of them “were nevertheless classified” as belonging to one of these four depression biotypes — suggesting an overlap between conditions."