As psychologists who have long researched and argued for a dimensional view of psychosis, we would like to comment on Lawrie et al's editorial.¹ We are surprised that the authors pay no attention – with one exception – to the psychological literature. If they had done so they would know that considerable evidence supporting the continuum view has accrued over many decades. The one psychologist they do cite – the late Paul Meehl – is an unfortunate choice. Quite apart from the fact that it is unclear to us how Meehl's taxonomic (categorical) approach actually helps their case, the authors ought to be aware that the theory is now on the wane. A more viable alternative is what we have termed a ‘fully dimensional’ theory that is capable of encompassing more of the known facts about psychosis, including the clear dimensionality of the risk of illness and the likely form of the heritability underpinning this, coupled with the notion of discontinuity to recognise the break in behaviour and psychological state that occurs when vulnerability translates into clinical symptoms. Importantly, the model also recognises something that Lawrie et al entirely ignore – the fact that psychotic traits can have a healthy expression that takes the individual outside the domain of psychiatric judgement.

Of course, many questions remain, such as how to deal with the overlap between schizophrenic and affective expressions of psychosis, explain the underlying biological mechanisms of these disorders, and incorporate into our thinking how expressions of vulnerability can vary from sick to benign. However, answers to these questions will not make dimensionality go away, for it is part of the essence of human variability (of which psychosis is one form).

On the practical front, these ideas admittedly make for a messy picture that is inconvenient for clinicians seeking a neat solution to diagnostic issues. But psychiatry does itself no favours by ignoring them and retreating (yet again) behind the ramparts of its traditional mode of thinking. Fortunately, as Lawrie et al will be aware, their profession actually has moved forward in recent years towards an attempt to find ways of integrating both dimensional and categorical perspectives into its future diagnostic systems. Our plea is that, in doing so, it becomes an even more ‘psychologically informed’ psychiatry.