Yuting Li, Minglan Yu, He Yang, Lu Shi, Tingting Wang, Rongfang He, Kezhi Liu, Wei Dong, Xuemei Liang, Bo Xiang
15 min
Schizophrenia is characterized by both positive symptoms (e.g., hallucinations) and negative symptoms (e.g., social withdrawal, blunted affect, and avolition). While antipsychotic medications effectively manage positive symptoms, they often fail to address negative symptoms, which are major drivers of functional impairment. This systematic review and network meta-analysis evaluated the efficacy of adding various antidepressants to existing antipsychotic regimens to treat these persistent negative symptoms.
The authors conducted a comprehensive search of PubMed and Web of Science for randomized, double-blind, placebo-controlled trials published up to April 2025. They included 15 studies involving 655 patients. The primary outcome was the change in negative symptom scores, measured using standardized scales like the Scale for the Assessment of Negative Symptoms (SANS) or the Positive and Negative Syndrome Scale (PANSS-N).
The meta-analysis found that adjunctive antidepressant treatment is superior to placebo in reducing negative symptoms. Specifically, mirtazapine and duloxetine emerged as the most effective options. Mirtazapine showed statistically significant superiority over placebo and outperformed several other antidepressants, including reboxetine, escitalopram, and bupropion. Duloxetine also demonstrated significant efficacy compared to placebo. The authors suggest that the mechanism of action for these two drugs—specifically their effects on serotonin and norepinephrine receptors—may be particularly relevant for addressing the underlying pathophysiology of negative symptoms.
Negative symptoms represent a significant, often unaddressed therapeutic gap in schizophrenia care that profoundly impacts a patient's ability to work and maintain social relationships. These findings provide clinicians with evidence-based options for augmenting standard antipsychotic treatment. By identifying mirtazapine and duloxetine as potentially effective adjunctive therapies, this research offers a promising strategy for improving the quality of life for patients who do not respond to antipsychotics alone.
BACKGROUND: The treatment response for the negative symptoms of schizophrenia is not ideal, and the efficacy of antidepressant treatment remains a matter of considerable controversy. This systematic review and meta-analysis aimed to assess the efficacy of adjunctive antidepressant treatment for negative symptoms of schizophrenia under strict inclusion criteria. METHODS: A systematic literature search (PubMed/Web of Science) was conducted to identify randomized, double-blind, effect-focused trials comparing adjuvant antidepressants with placebo for the treatment of negative symptoms of schizophrenia from database establishment to April 16, 2025. Negative symptoms were examined as the primary outcome. Data were extracted from published research reports, and the overall effect size was calculated using standardized mean differences (SMD). RESULTS: = 64, SMD -1.19, CI -2.17, -0.21) showed significantly better efficacy for negative symptoms compared to placebo. In direct comparisons between antidepressants, mirtazapine showed significant differences compared to reboxetine, escitalopram, and bupropion, but there were no significant differences between other antidepressants or between antidepressants and placebo. No publication bias for the prevalence of this condition was observed. CONCLUSIONS: These findings suggest that adjunctive use of mirtazapine and duloxetine can effectively improve the negative symptoms of schizophrenia in patients who are stably receiving antipsychotic treatment. Therefore, incorporating antidepressants into future treatment plans for negative symptoms of schizophrenia is a promising strategy that warrants further exploration.
Sam: So rather than suppressing an overactive circuit, they're acting directly on the circuits tied to motivation and affect.
Alex: That's the proposed logic, yes. It's plausible, and it fits with why dopamine-focused antipsychotics have been such a poor match for this symptom domain for decades. [[RP_SECTION:evidence-base-limitations|Evidence base limitations]]
Sam: Plausible is doing some work in that sentence, though. How many trials are actually behind the mirtazapine ranking specifically? If it's one or two studies driving that 1.73, the confidence interval around it is going to be wide.
Alex: You're right to flag that. The authors are upfront that some of these rankings rest on a small number of trials per drug, which limits precision and makes the point estimate more fragile than the headline number suggests. This isn't a failure of the method — a network meta-analysis is doing legitimate work synthesizing what exists — but the underlying evidence base is thin. There's no preregistered mega-trial here, no dose-response testing, and no look at whether the benefit holds over longer follow-up. [[RP_SECTION:clinical-implications-and-future|Clinical implications and future]]
Sam: So it's less "we've found the answer" and more "we've built the best possible synthesis of a small, scattered literature."
Alex: That's a fair way to put it. It gives clinicians and trialists a ranked, evidence-based starting point rather than a guess, but it's not the kind of result that should shift prescribing on its own — it tells the field where to point the next, larger trial.
Sam: A meaningful step forward, then, not yet a verdict.
Alex: If you want the figures and the method choices we skipped, you can generate a deep dive of this paper. The paper has the rest either way.
Sam: Thanks for listening.