The expatriate Australian psychiatrist, Barney Carroll, wrote that to understand depression is to understand psychiatry (Carroll, 1989). ‘Depression’ presents the greatest challenges and the greatest risk of hubris. It is a fantasy to imagine that a clear-cut typology either exists or can be readily derived, and the road to that castle is littered with numerous classificatory systems, variably proposed by observant clinicians and/or opinionated academics. The opinionated are now regressed to the mean by Consensus Committee processes, a theoretically constructive strategy but one that is disappointing in practice because of their reliance on formal evidence-based data while their risk-free ambience tends to reify the orthodox.

The previous chapter considered how ‘clinical depression’ can be defined, differentiated (phenomenologically from grief and anxiety), and diagnosed – all relatively straightforward issues in comparison to this chapter's domain. Here we seek to tackle a more difficult task: considering whether meaningful depressive disorders can be differentiated or cleaved from each other, whether such differentiation is absolute or a matter of degree (i. e. independence or interdependence), and then present a differentiated model (of ‘meaningful’ depressive conditions) which, we argue, allows differential treatment approaches to be provided on a more rational basis.

It is in our nature as human beings to seek simple models to assist us through life and, if a simple taxonomy did have explanatory power, we would all be most appreciative.