However, the story appears to be a bit more complex, because the biological cause does not materialize suddenly in a vacuum. I think what Borsboom et al are suggesting is to look for feedback loops in a kind of circular causality. Thus, pointing to one cause only makes partial sense, because you could partition the stream of events differently. In the short example by Rachel777, theories about the cause and treatment of ‘depression’ leads to an intervention with antidepressants, which leads to a new dynamic for maintaining the ‘depressive state’ by influencing processes in the gut. This, however, could not have been the initial cause for the ‘depression’ simply because it must be assumed the ‘depression’ preceded the antidepressants. Thus, the *cause* of the ‘depression’ could equally validly be processes resulting in the initial symptoms, the idea of treating ‘depression’ with antidepressants, the side effects of the antidepressant or the B12 deficiency. More correctly, I think, the whole sequence of events could be considered, and one or more strategic points of intervention pursued in a necessary collaboration with the person experiencing the difficulties. The work of Borsboom et al is very interesting, I think, and part of a renewed interest in using (holistic) systems thinking in the context of mental health, which could actually make a sensible difference. In a later comment you write, that it is untrue that ‘mental health concerns are not brain disorders’ because biological causation may lead to mental health concerns. However, from a systemic process point of view it is still true, I think, that ‘mental disorders’ cannot primary be understood as brain disorders, because the causality involved is much more complex and traverses different levels of description. Unfortunately this flies in the face of hopes for a ‘simple’, one-domain solution to mental health problem, which is what many are hoping for (and which would be nice if true). The Borsboom et al perspective paints a differently complex picture.