Abstract: The aim of this study was to investigate the long-term effectiveness and efficacy of haloperidol, risperidone and olanzapine in first-episode schizophrenia-spectrum disorders. This was a prospective, randomized, open-label study. Data for the present investigation were obtained from a large epidemiological and 3-year longitudinal intervention programme of first-episode psychosis conducted at the University Hospital Marques de Valdecilla, Santander, Spain. One hundred and seventy-four patients were randomly assigned to haloperidol (N?=?56), olanzapine (N?=?55), or risperidone (N?=?63) and followed up for 1 year. The primary effectiveness measure was all causes of treatment discontinuation. Effectiveness analyses were based on intend-to-treat populations. In addition, an analysis based on per protocol populations was conducted in the analysis for clinical efficacy. The treatment discontinuation rate for any cause was higher with haloperidol than with risperidone and olanzapine (?2?=?8.517; p?=?0.014). The difference in discontinuation rate between risperidone and olanzapine was not significant (?2?=?0.063; p?=?0.802). There were no significant advantages of any of the three treatments in reducing the severity of psychopathology. Risperidone and olanzapine demonstrated higher effectiveness relative to haloperidol, but the three antipsychotics were equally effective in reducing the severity of psychopathology. Specific clinical programmes and the use of second-generation antipsychotics may enhance the effectiveness of antipsychotic treatments.
