Within the field of psychopathology, several diagnostic classification systems are used, of which the International Classification of Diseases and Related Health Problems (ICD) and the Diagnostic and Statistical Manual of Mental Disorders are the current dominant frameworks. Even though both manuals classify similar mental and behavioural disorders, research shows that there are striking difference in concordance and prevalence of disorders depending on which manual (or manual-based instrument) is used. In this paper we investigated the symptom structure of the ICD-10 and DSM-IV-TR by representing individual symptoms are nodes and connecting nodes whenever the corresponding symptom feature as diagnostic criteria for the same mental disorder. Additionally we investigated whether this symptom network structure aligns with empirical data.

Results indicate that, relative to the DSM-IV-TR network, the ICD-10 network contains (a) more nodes, (b) lower level of clustering, and (c) a higher level of connectivity. Nevertheless, the nodes that are most central to each networks are very similar. Comparison to empirical data indicates that the DSM-IV-TR network structure follows comorbidity rates more closely than the ICD-10 network structure. We conclude that, despite their apparent likeness, ICD-10 and DSM-IV-TR harbour important structural differences, and that both may be improved by matching diagnostic categories more closely to empirically determined network structures.