Abstract: We included six trials (n = 698; most participants were women approximately 40 years of age). All studies evaluated psychotherapy plus usual care (with antidepressants) versus usual care (with antidepressants). Three studies addressed the addition of cognitive-behavioural therapy (CBT) to usual care (n = 522), and one each evaluated intensive short-term dynamic psychotherapy (ISTDP) (n = 60), interpersonal therapy (IPT) (n = 34), or group dialectical behavioural therapy (DBT) (n = 19) as the intervention. Most studies were small (except one trial of CBT was large), and all studies were at high risk of detection bias for the main outcome of self-reported depressive symptoms. A random-effects meta-analysis of five trials (n = 575) showed that psychotherapy given in addition to usual care (vs usual care alone) produced improvement in self-reported depressive symptoms (MD -4.07 points, 95% confidence interval (CI) -7.07 to -1.07 on the Beck Depression Inventory (BDI) scale) over the short term (up to six months). Effects were similar when data from all six studies were combined for self-reported depressive symptoms (SMD -0.40, 95% CI -0.65 to -0.14; n = 635). The quality of this evidence was moderate. Similar moderate-quality evidence of benefit was seen on the Patient Health Questionnaire-9 Scale (PHQ-9) from two studies (MD -4.66, 95% CI 8.72 to -0.59; n = 482) and on the Hamilton Depression Rating Scale (HAMD) from four studies (MD -3.28, 95% CI -5.71 to -0.85; n = 193). High-quality evidence shows no differential dropout (a measure of acceptability) between intervention and comparator groups over the short term (RR 0.85, 95% CI 0.58 to 1.24; six studies; n = 698). Moderate-quality evidence for remission from six studies (RR 1.92, 95% CI 1.46 to 2.52; n = 635) and low-quality evidence for response from four studies (RR 1.80, 95% CI 1.2 to 2.7; n = 556) indicate that psychotherapy was beneficial as an adjunct to usual care over the short term. With the addition of CBT, low-quality evidence suggests lower depression scores on the BDI scale over the medium term (12 months) (RR -3.40, 95% CI -7.21 to 0.40; two studies; n = 475) and over the long term (46 months) (RR -1.90, 95% CI -3.22 to -0.58; one study; n = 248). Moderate-quality evidence for adjunctive CBT suggests no difference in acceptability (dropout) over the medium term (RR 0.98, 95% CI 0.66 to 1.47; two studies; n = 549) and lower dropout over long term (RR 0.80, 95% CI 0.66 to 0.97; one study; n = 248). Two studies reported serious adverse events (one suicide, two hospitalisations, and two exacerbations of depression) in 4.2% of the total sample, which occurred only in the usual care group (no events in the intervention group). An economic analysis (conducted as part of an included study) from the UK healthcare perspective (National Health Service (NHS)) revealed that adjunctive CBT was cost-effective over nearly four years. Moderate-quality evidence shows that psychotherapy added to usual care (with antidepressants) is beneficial for depressive symptoms and for response and remission rates over the short term for patients with TRD. Medium- and long-term effects seem similarly beneficial, although most evidence was derived from a single large trial. Psychotherapy added to usual care seems as acceptable as usual care alone. Further evidence is needed on the effectiveness of different types of psychotherapies for patients with TRD. No evidence currently shows whether switching to a psychotherapy is more beneficial for this patient group than continuing an antidepressant medication regimen. Addressing this evidence gap is an important goal for researchers.

Plain-language summary: We included six randomised trials (studies in which participants are allocated at random (by chance) to receive one of the treatments being compared). These trials included 698 people and tested three different types of psychotherapy. All studies looked at whether adding psychotherapy to current medical treatment leads to improvement in depression. All studies were funded by public research grants. We found that patients who receive psychotherapy as well as usual care with antidepressants had fewer depressive symptoms and were more often depression-free six months later compared with patients who continued with usual care alone. We are moderately confident of these findings, which means that the true effect of adding CBT may be different from what we found, although findings are likely to be close. We also found that added psychotherapy was as acceptable to patients as usual care alone. Two studies noted similar beneficial effects after 12 months, and one study at 46 months. Two studies reported harmful effects in people receiving usual care alone (one suicide, two people hospitalised) but none in people receiving psychotherapy in addition to usual care. Because participants were aware of the treatment they had received, and because we identified only a small number of studies, we graded the evidence as moderate in quality for findings at six months and low in quality for long-term results. This assessment might change in the future, if higher-quality research results become available.