The concept of positive and negative symptoms in schizophrenia can be traced back to Hughlings Jackson (1889) who taught that disease does not create, it sets free, and accordingly positive symptoms could be seen as ‘release’ phenomena resulting from ‘dissolution’ of the highest cerebral centres of the nervous system. Crow (1980) revived the dichotomy and proposed a Type I syndrome, characterised by positive symptoms, and a Type II syndrome, characterised by negative symptoms. He thought the latter was due to cortical atrophy and responded poorly to antipsychotic medication. In their review of the distinction, Walker & Lewine (1988) found a stronger relationship between premorbid dysfunction and negative symptoms than with positive symptoms. They also found there was a stronger influence of genetic factors on negative symptoms than positive symptoms.