this is the title of a book by Roth and Fonagy (2005) published by Guilford Press. The authors answer this question with a focus on disorders. Their conclusions inform the NICE Guidelines.
By contrast the contributors to ‘Drop the Disorder!’ edited by Jo Watson (2019) recommend jettisoning disorder in favour of formulation. However there has been no determination of ‘what works for whom?’ where the focus is formulation. Indeed it is impossible to do this as formulations are inherently unique/idiosyncratic theories about an individual. It is an attempt to personalise treatment without first acknowledging that the person is likely a member of some category or categories. Ironically it is personalised medicine without first getting into the right ball-park. For the past decade the IAPT (Improving Access to Psychological Treatments) service has been an undercover exemplar of this, paying lip service to the NICE Guidelines. If IAPT had truly done ‘what it says on the tin’, it would have ‘improved’ upon on Roth and Fonagy’s work. But it has signally failed to make any contribution to the question they raised. .
Dalgleish et al (2020) in their just published paper a Transdiagnostic. Approach to Mental Health Problems http://dx.doi.org/10.1037/ccp0000482 advocate a ‘hard transdiagnostic’ approach, similarly wishing to totally jettison the diagnostic nomenclature of DSM-5. But this hard trans diagnostic approach is so bewildering in its’ complexity, it would serve only to totally muddle practitioners. There is no evidence that trans diagnostic approaches add value. To date studies have only been conducted by the developers of the trans diagnostic approaches, leading to likely allegiance bias. There are no effectiveness studies in real world settings with independent evaluators.
Dr Mike Scott