Mirtazapine add-on therapy in the treatment of schizophrenia with atypical antipsychotics: a double-blind, randomised, placebo-controlled clinical trial.

Objective: Schizophrenia is a multifaceted illness with positive, negative and cognitive symptom domains. Standard treatments often focus on positive symptoms and may not adequately relieve other symptoms. Previous studies have suggested a role for mirtazapine in schizophrenia, particularly in negative symptoms. This study investigates the efficacy of adding mirtazapine to treatment as usual to alleviate the negative symptoms of schizophrenia.

Methods: In a 6 week, double-blind clinical trial, participants with a diagnosis of schizophrenia and currently being treated with atypical antipsychotic medication were randomised to adjunctive treatment with mirtazapine (30 mg/day) or placebo. The primary outcome measure was improvement in the Positive and Negative Syndrome Scale (PANSS). Measures of cognition, collected at baseline and week 6 only, were analysed using an Analysis of Covariance (ANCOVA) model. All other outcome measures were analysed using a linear mixed model.

Results: Forty participants were recruited to the study with equal numbers randomised to each treatment arm. There was no significant difference between mirtazapine and placebo treated participants for improvement in PANSS scores or any of the secondary outcome measures at any stage during the 6-week trial.

Conclusions: This trial does not confirm previous research supporting the use of mirtazapine adjunctive to atypical antipsychotic treatment for schizophrenia.