Three Kinds Of Depression

[S]cientists collected clinical, biological, and life history data from 134 individuals -- half of whom were newly diagnosed with depression and the other half who had no depression diagnosis- using questionnaires and blood tests. Participants were asked about their sleep patterns, whether or not they had stressful issues, or other mental health conditions. Researchers also scanned participants' brains using magnetic resonance imaging (MRI) to map brain activity patterns in different regions. . . . 

[T[he researchers identified a group of closely-placed data clusters, which consisted of measurable features essential for accessing mental health of an individual. Three out of the five data clusters were found to represent different sub-types of depression. 

The three distinct sub-types of depression were characterized by two main factors: functional connectivity patterns synchronized between different regions of the brain and childhood trauma experience. They found that the brain's functional connectivity in regions that involved the angular gyrus -- a brain region associated with processing language and numbers, spatial cognition, attention, and other aspects of cognition -- played a large role in determining whether SSRIs were effective in treating depression. 

Patients with increased functional connectivity between the brain's different regions who had also experienced childhood trauma had a sub-type of depression that is unresponsive to treatment by SSRIs drugs, the researchers found. On the other hand, the other two subtypes -- where the participants' brains did not show increased connectivity among its different regions or where participants had not experienced childhood trauma -- tended to respond positively to treatments using SSRIs drugs. 

This study not only identifies sub-types of depression for the first time, but also identifies some underlying factors and points to the need to explore new treatment techniques.

From here. The paper discussed above is:

Tomoki Tokuda, et al., "Identification of depression subtypes and relevant brain regions using a data-driven approach." 8(1) Scientific Reports 14082 (2018) (open access). DOI: 10.1038/s41598-018-32521-z

The money chart is here.

The study also makes findings about the two key binary factors identified and remission:

For the relationship between CATS and remission, our finding is consistent with the meta analysis of previous studies38, which clearly suggests that experiences of child abuse trauma have a negative impact on treatment of depression. The contribution of our study in this regard is that we were able to identify among a huge number of possible associations this specific association in an unsupervised manner without prior knowledge of feature selection. As for the medical causal relationship, recent studies suggest that treatment-resistant depression may be linked to release of pre-inflammatory cytokines, which can be caused by childhood adversity39,40. However, in our research framework, biomarkers of inflammation were not included, which prevents us from confirming this point. 

Concerning the key role of the angular gyrus (AG) in predicting remission, our finding is consistent with the results of a t-test on differences between TRD and non-TRD18,19. Unfortunately, these two previous studies are contradictory because the former study suggests that a higher FC is associated with TRD, while the latter study found that a lower FC is associated with TRD. Our result supports the former study. Moreover, recent studies have revealed that AG is related to several functions, such as semantic processing, default mode network, number processing, attention and spatial cognition, and memory retrieval41. Such multiple functions of AG are consistent with an fMRI study42, which suggests that AG is one of the major connecting hubs, together with the occipital and ventral-medial parietal. Nonetheless, these results of previous studies do not adequately explain the possible association between AG and remission of depression implied in our study. Further research is required for clarification of this point, which may provide useful insights into possible treatment of depressive patients by means of neurofeedback.

The paper sheds little insight on what distinguished the two clusters of control subject from each other that I could discern from reading the paper and the supplemental materials.