Antidepressants for the negative symptoms of schizophrenia

Negative symptoms are common in people with schizophrenia and are often difficult to treat with antipsychotic drugs. Treatment often involves the use of various add-on medications such as antidepressants.

To review the effects of the combination of antipsychotic and antidepressant drug treatment for management of negative symptoms in schizophrenia and schizophrenia-like psychoses.

We searched the Cochrane Schizophrenia Group's register (January 2004). We also contacted authors of included studies in order to identify further trials.

We included all randomised controlled trials comparing antipsychotic and antidepressant combinations with antipsychotics alone for the treatment of prominent negative symptoms in schizophrenia and/or schizophrenia-like psychoses.

Working independently, we selected and critically appraised studies, extracted data and analysed on an intention-to-treat basis. Where possible and appropriate we calculated the relative risk RR) and their 95% confidence intervals (CI), with the number needed to treat (NNT).

We included five studies (all short-term, total N=190). We found no significant difference for 'leaving the study early for any reason' between the antipsychotic plus antidepressant combination and the control group (n=90, 3 RCTs, RR 3.0 CI 0.35 to 26.04). Leaving early due to adverse events (n=64, 2 RCTs, RR 5.0 CI 0.26 to 97.0) and leaving the study early due to inefficacy (n=34, 1 RCT, RR 3.0 CI 0.13 to 68.84) also showed no significant difference between the two treatment groups. In terms of clinical response, participants treated with the antipsychotic plus antidepressant medications showed a statistically significant greater improvement (n=30, 1 RCT, WMD -1.0 CI -1.61 to -0.39) and showed a significantly lower severity at endpoint (n=30, 1 RCT, WMD -0.9 CI -1.55 to -0.25) on the Clinical Global Impression Scale than those treated with antipsychotics alone. More people allocated to combination therapy had a clinically significant improvement in negative symptoms compared with those given antipsychotics and placebo (n=60, 2 RCTs, RR 0.56 CI 0.32 to 0.97, NNT 3 CI 3 to 34). Significant differences in favour of the combination therapy were seen in different aspects of negative symptoms: 'affective flattening' (n=30, 1 RCT, WMD -7.0 CI -10.37 to -3.63), 'alogia' (n=26, 1 RCT, WMD -3.00 CI -5.14 to -0.86) and 'avolition' (n=30, 1 RCT, WMD -3.0 CI -5.04 to -0.96). No statistically significant difference was found between treatment groups in regards to the outcome 'at least one adverse event' (n=84, 2 RCTs, RR 1.80 CI 0.66 to 4.90). For movement disorders and other adverse effects, no statistically significant differences were found in any of the studies that provided usable data on these outcomes. There are no data at all on outcomes such as compliance, cost, social and cognitive functioning, relapse, recurrence of negative symptoms, rehospitalisation or quality of life. There are no medium or long term data.

The combination of antipsychotics and antidepressants may be effective in treating negative symptoms of schizophrenia, but the amount of information is currently too limited to allow any firm conclusions. Large, pragmatic, well-designed and reported long term trials are justified.