Fig. 2.

Comorbidity under a network approach. Disorder 1 consists of bidirectionally related symptoms X1–X5, and disorder 2 consists of symptoms Y1–Y5. Symptoms B1 and B2 are bridge symptoms that overlap between disorders 1 and 2. In this model, comorbidity arises as a result of direct relations between the bridge symptoms of two disorders (Figure from Cramer et al. [21] with minor adjustments; reprinted with permission)