This critical review searched for literature concerning duration of untreated psychosis published up to 2004, finding 43 publications that were carried over into the meta-analysis.[Perkins et al., 2005]
Whilst a shorter duration of untreated psychosis was associated with greater response to antipsychotic treatment (as measured by severity of global psychopathology, positive symptoms, negative symptoms, and functional outcomes), duration of untreated psychosis was associated only with the severity of negative symptoms – not severity of global psychopathology, positive symptoms, or neurocognitive functioning.[Perkins et al., 2005]
Reference:
Perkins DO, Gu H, Boteva K, Lieberman JA. Relationship between duration of untreated psychosis and outcome in first-episode schizophrenia: a critical review and meta-analysis. Am J Psychiatry 2005; 162 (10): 1785–1804.