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Researchers at the University of Amsterdam (UvA) have developed a new explanation for mental disorders such as depression.

Researchers at the University of Amsterdam (UvA) have developed a new explanation for mental disorders such as depression. They interpret a mental disorder as a network of symptoms, rather than a specific biological abnormality. This network approach could offer an explanation for the fact that although mental disorders like depression are to a large extent hereditary, nobody so far has been able to find the 'depression gene'. The findings of the UvA researchers were published on 30 June 2010 on the Behavioral and Brain Sciences website.

According to the prevailing view, direct relationships between symptoms do not matter. There is, after all, a biological cause that explains the origin of all symptoms. In the case of depression, an oft-heard assumption is, for example, that such symptoms of depression are caused by serotonin deficiency in the brain. Contrary to this view, the UvA researchers present a network approach in which a mental disorder is not viewed as a biological abnormality, but as a network of symptoms that are directly linked.

This seems intuitively logical. Two symptoms of depression are, for example, sleep deprivation and fatigue. In this case, it seems more sensible to assume there is a direct link between these symptoms (i.e. if you do not sleep, you become tired) than to interpret this relationship as having a biological cause. This view is consistent with the increasingly obvious evidence that symptoms of a mental disorder cannot be explained by a specific biological abnormality. This vision also fits the intuitive notion that people are likely to differ greatly in how they are actually depressed.

The network model

The researchers comment critically on existing ideas and present an alternative network model. In addition, they show, in the case of the comorbidity between depression and generalised anxiety, that direct relationships between symptoms can be very different in strength. This means that some paths to commorbidity are more likely than others. It also means that some symptoms are 'more dangerous' than others; if someone has a symptom that is strongly associated with other symptoms from the network, then that is a 'dangerous' symptom because someone has an increased chance of also exhibiting other symptoms (because of the strong connections).

Publication details

Cramer, A. O. J., Waldorp, L. J., Van der Maas, H. and Borsboom, D. Comorbidity: A network perspective. Behavioral and Brain Sciences 33, 137-193.