The negative symptoms of schizophrenia: category or continuum?

Negative symptoms have been considered to be specific to schizophrenia or a subtype of schizophrenia: the deficit syndrome. In other words, these symptoms have been considered to be categorically different from other forms of human behavior and experience, whether they occur in healthy persons or patients with other psychiatric disorders. In this paper, we advocate a dimensional approach to negative symptoms, which is supported by two main arguments. First, enduring negative symptoms can even be observed in a variety of psychiatric disorders and they are not specific to schizophrenia. Second, we review evidence that negative symptoms show a continuous distribution from apparently healthy subjects to those with a fully developed clinical syndrome. Although the evidence does not allow for a definite decision concerning the dimensional distribution of negative symptoms, it certainly justifies exploring a dimensional approach with respect to its clinical and scientific utility. Understanding negative symptoms as a variation of normal mental processes will strengthen the development of neurocognitive models and treatment approaches.