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

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.