• Angelo Barbato, Barbara D'Avanzo, and Alberto Parabiaghi.
• Unit for quality of care and rights promotion in mental health, Department of Neuroscience, IRCCS-Istituto di Ricerche Farmacologiche Mario Negri, Via La Masa 19, Milano, Italy, 20156.
• Cochrane Db Syst Rev. 2018 Jun 8; 6: CD004188.

BackgroundCouple therapy for depression has the twofold aim of modifying negative interaction patterns and increasing mutually supportive aspects of intimate relationships, changing the interpersonal context of depression. Couple therapy is included in several guidelines among the suggested treatments for depression.Objectives1. The main objective was to examine the effects of couple therapy compared to individual psychotherapy for depression.2. Secondary objectives were to examine the effects of couple therapy compared to drug therapy and no/minimal treatment for depression.Search MethodsThe Cochrane Common Mental Disorders Group Controlled Trials Register (CCMDCTR), the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE (Ovid), Embase (Ovid) and PsycINFO (Ovid) were searched to 19 February 2018. Relevant journals and reference lists were checked.Selection CriteriaRandomised and quasi-randomised controlled trials examining the effects of couple therapy versus individual psychotherapy, drug therapy, or no treatment/minimal treatment for depression were included in the review.Data Collection And AnalysisWe considered as primary outcomes the depressive symptom level, the depression persistence, and the dropouts; the relationship distress level was a secondary outcome. We extracted data using a standardised spreadsheet. Where data were not included in published papers, we tried to obtain the data from the authors. We synthesised data using Review Manager software version 5.3. We pooled dichotomous data using the relative risk (RR), and continuous data calculating the standardised mean difference (SMD), together with 95% confidence intervals (CIs). We employed the random-effects model for all comparisons and also calculated a formal test for heterogeneity, the natural approximate Chi2 test.Main ResultsWe included fourteen studies from Europe, North America, and Israel, with 651 participants. Eighty per cent of participants were Caucasian. Therefore, the findings cannot be considered as applicable to non-Western countries or to other ethnic groups in Western countries. On average, participants had moderate depression, preventing the extension of results to severely depressed patients. Almost all participants were aged between 36 and 47 years.There was no evidence of difference in effect at the end of treatment between couple therapy and individual psychotherapy, either for the continuous outcome of depressive symptoms, based on nine studies with 304 participants (SMD -0.17, 95% CI -0.44 to 0.10, low-quality evidence), or the proportion of participants remaining depressed, based on six studies with 237 participants (RR 0.94, 95% CI 0.72 to 1.22, low-quality evidence). Findings from studies with 6-month or longer follow-up confirmed the lack of difference between the two conditions.No trial gave information on harmful effects. However, we considered rates of treatment discontinuation for any reason as a proxy indicator of adverse outcomes. There was no evidence of difference for dropout rates between couple therapy and individual psychotherapy, based on eight studies with 316 participants (RR 0.85, 95% CI 0.51 to 1.41, low-quality evidence).Few data were available for the comparison with drug therapy. Data from a small study with 12 participants showed no difference for the continuous outcome of depressive symptoms at end of treatment (SMD -0.51, 95% CI -1.69 to 0.66, very low-quality evidence) and at 6-month follow-up (SMD -1.07, 95% CI -2.45 to 0.31, very low-quality evidence). Data on dropouts from two studies with 95 participants showed a clear advantage for couple therapy (RR 0.31, 95% CI 0.15 to 0.61, very low-quality evidence). However, this finding was heavily influenced by a single study, probably affected by a selection bias favouring couple therapy.The comparison between couple therapy plus drug therapy and drug therapy alone showed no difference in depressive symptom level, based on two studies with 34 participants (SMD -1.04, 95% CI -3.97 to 1.89, very low-quality evidence) and on dropouts, based on two studies with 45 participants (RR 1.03, 95% CI 0.07 to 15.52, very low-quality evidence).The comparison with no/minimal treatment showed a large significant effect favouring couple therapy both for depressive symptom level, based on three studies with 90 participants: (SMD -0.95, 95% CI -1.59 to -0.32, very low-quality evidence) and persistence of depression, based on two studies with 65 participants (RR 0.48, 95% CI 0.32 to 0.70, very low-quality evidence). No data were available for dropouts for this comparison.Concerning relationship distress, the comparison with individual psychotherapy showed that couple therapy appeared more effective in reducing distress level at the end of treatment, based on six studies with 187 participants (SMD -0.50, CI -0.97 to -0.02, very low-quality evidence) and the persistence of distress, based on two studies with 81 participants (RR 0.71, 95% CI 0.51 to 0.98, very low-quality evidence). The quality of evidence was heavily affected by substantial heterogeneity (I2 = 59%). In the analysis restricted to studies including only distressed couples, no heterogeneity was found and the effect in distress level at the end of treatment was larger (SMD -1.10, 95% CI -1.59 to -0.61). Very few data on this outcome were available for other comparisons.We assessed the certainty of the evidence using the GRADE system. The results were weakened by the low quality of evidence related to the effects on depressive symptoms, in comparison with individual psychotherapy, and by very low quality evidence for all other comparisons and for the effects on relationship distress. Most studies were affected by problems such as the small number of cases, performance bias, assessment bias due to the non-blinding outcome assessment, incomplete outcome reporting and the allegiance bias of investigators. Heterogeneity was, in particular, a problem for data about relationship distress.Authors' ConclusionsAlthough there is suggestion that couple therapy is as effective as individual psychotherapy in improving depressive symptoms and more effective in improving relations in distressed couples, the low or very low quality of the evidence seriously limits the possibility of drawing firm conclusions. Very few data were available for comparisons with no/minimal treatment and drug therapy. Future trials of high quality should test in large samples with a long follow-up of the effects of couple therapy in comparison to other interventions in discordant couples with a depressed partner, considering the role of relationship quality as a potential effect mediator in the improvement of depression.

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