Psychological Medicine


Why we need more debate on whether psychotic symptoms lie on a continuum with normality

A. S. Davida1 c1

a1 Section of Cognitive Neuropsychiatry, Institute of Psychiatry, King's College, London, UK

The notion that psychotic symptoms lie on a continuum with normality has become an accepted dogma. It is supported by several lines of empirical evidence, fits in with the orientation of modern services and has a ‘moral’ appeal. However, there is confusion as to the nature of the continuum or continua under discussion. According to the author, commentators on this topic do not often distinguish between the variability and severity of the phenomena themselves, within or between individuals, versus the distribution of symptoms or risk factors in a population. The implications of these two types of continua differ. Furthermore, the evidence for continua of delusional beliefs and hallucinations can be challenged on a number of grounds, both methodological and conceptual. To some extent, whether phenomena are viewed as continua or categories depends on the intentions of the observer. Finding the distinctive characteristics of psychotic phenomena in people with clinical disorders, in addition to their origins in ‘normal’ cognitive processes, is a worthwhile goal.

(Received July 28 2009)

(Revised January 05 2010)

(Accepted January 11 2010)

(Online publication February 11 2010)


c1 Address for correspondence: A. S. David, M.D., FRCP, FRCPsych., M.Sc., Section of Cognitive Neuropsychiatry, PO Box 68, Institute of Psychiatry, King's College, Denmark Hill, London SE5 8AF, UK. (Email: