Figure 2.

Example of a multilayer human system network, encoding information about psychology (symptom network), biology (brain network), and environment (social network), and the interlayer links between them. Figure adapted from (88). A multilayer network framework that incorporates possible mechanisms beyond symptoms may offer additional explanatory insight in biological psychiatry. For example, densely connected symptom networks is associated with greater vulnerability to develop psychopathology (89,90) than less-dense networks. Similarly, many psychiatric disorders share brain network alterations in functional connectivity (e.g., altered functional connectivity in the default mode network has been observed in Alzheimer disease, autism, schizophrenia, depression, and epilepsy (91,92). Considering the social network layer, living alone and away from family have been observed in alcohol dependence (93) and low and high depressive symptoms have been strongly correlated with such scores in friends and neighbors (94). A multilayer network approach that integrates psychological, biological, and environmental can offer insight into shared and distinct features in each layer across psychiatric disorders. In this way, a multilayer network framework can identify common targets for intervention, be it in symptom, brain, or social networks as well as offer insight into explanations for psychiatric comorbidity.