The progression of schizophrenia and functional decline

In most patients, the formal onset of schizophrenia is preceded by a period of symptoms, known as the prodromal period.^{[Lieberman et al., 2001]} Symptoms in this stage can include mood disturbances and cognitive symptoms, as well as positive symptoms.^{[Lieberman et al., 2001; McGlashan, 1996]} Treatment with antipsychotic therapy can ameliorate psychotic symptoms, and maintenance therapy is effective in preventing relapse.^{[Lieberman et al., 2001]} Because the clinical deterioration of schizophrenia may begin in the prodromal phase, early identification is important to allow timely intervention.^{[Lieberman et al., 2001; McGlashan, 1996]}

References:
Lieberman JA, Perkins D, Belger A, et al. The early stages of schizophrenia: speculations on pathogenesis, pathophysiology, and therapeutic approaches. Biol Psychiatry 2001; 50 (11): 884–897.

McGlashan TH. Early detection and intervention in schizophrenia: research. Schizophr Bull 1996; 22 (2): 327–345.