Study designs of evaluations included in the review
Randomised, double-blinded, parallel-group trials were eligible for inclusion.
Specific interventions included in the review
Placebo-controlled studies that compared SSRI add-on therapy with antipsychotic treatment were eligible for inclusion. Studies on monoamino oxidase inhibitors, or tricyclic, dual-action or atypical antidepressants were excluded. The SSRIs assessed in the included studies were fluoxetine, fluvoxamine, sertraline, citalopram and paroxetine. The antipsychotics, where reported, were clozapine, olanzapine, typical antipsychotics or mixed antipsychotics. Treatment duration ranged from 4 weeks to 4 months.
Participants included in the review
Studies of patients with a diagnosis of schizophrenia-spectrum disorder were eligible for inclusion. Studies were excluded if schizophrenia patients were diagnosed with co-morbid obsessive-compulsive disorder. The patients in the included studies were chronic and non-chronic patients and in-patients and out-patients.
Outcomes assessed in the review
Studies that assessed negative symptoms using the Scale for the Assessment of Negative Symptoms (SANS) or the Positive and Negative Syndrome Scale-negative subscale (PANSS-N) before and after follow-up were eligible for inclusion. Studies with incomplete or unavailable data were excluded; authors were contacted for missing data.
How were decisions on the relevance of primary studies made?
Decisions on inclusion were achieved through consensus.