Background: Major depressive disorders have a significant impact on children and adolescents, including on educational and vocational outcomes, interpersonal relationships, and physical and mental health and well-being. There is an association between major depressive disorder and suicidal ideation, suicide attempts, and suicide. Antidepressant medication is used in moderate to severe depression; there is now a range of newer generations of these medications. Objectives: To investigate, via network meta-analysis (NMA), the comparative effectiveness and safety of different newer generation antidepressants in children and adolescents with a diagnosed major depressive disorder (MDD) in terms of depression, functioning, suicide-related outcomes and other adverse outcomes. The impact of age, treatment duration, baseline severity, and pharmaceutical industry funding was investigated on clinician-rated depression (CDRS-R) and suicide-related outcomes. Search methods: We searched the Cochrane Common Mental Disorders Specialised Register, the Cochrane Library (Central Register of Controlled Trials (CENTRAL) and Cochrane Database of Systematic Reviews (CDSR)), together with Ovid Embase, MEDLINE and PsycINFO till March 2020. Selection criteria: Randomised trials of six to 18 year olds of either sex and any ethnicity with clinically diagnosed major depressive disorder were included. Trials that compared the effectiveness of newer generation antidepressants with each other or with a placebo were included. Newer generation antidepressants included: selective serotonin reuptake inhibitors; selective norepinephrine reuptake inhibitors (SNRIs); norepinephrine reuptake inhibitors; norepinephrine dopamine reuptake inhibitors; norepinephrine dopamine disinhibitors (NDDIs); and tetracyclic antidepressants (TeCAs). Data collection and analysis: Two reviewers independently screened titles/abstracts and full texts, extracted data, and assessed risk of bias. We analysed dichotomous data as Odds Ratios (ORs), and continuous data as Mean Difference (MD) for the following outcomes: depression symptom severity (clinician rated), response or remission of depression symptoms, depression symptom severity (self-rated), functioning, suicide related outcomes and overall adverse outcomes. Random-effects network meta-analyses were conducted in a frequentist framework using multivariate meta-analysis. Certainty of evidence was assessed using Confidence in Network Meta-analysis (CINeMA). We used "informative statements" to standardise the interpretation and description of the results. Main results: Twenty-six studies were included. There were no data for the two primary outcomes (depressive disorder established via clinical diagnostic interview and suicide), therefore, the results comprise only secondary outcomes. Most antidepressants may be associated with a "small and unimportant" reduction in depression symptoms on the CDRS-R scale (range 17 to 113) compared with placebo (high certainty evidence: paroxetine: MD -1.43, 95% CI -3.90, 1.04; vilazodone: MD -0.84, 95% CI -3.03, 1.35; desvenlafaxine MD -0.07, 95% CI -3.51, 3.36; moderate certainty evidence: sertraline: MD -3.51, 95% CI -6.99, -0.04; fluoxetine: MD -2.84, 95% CI -4.12, -1.56; escitalopram: MD -2.62, 95% CI -5.29, 0.04; low certainty evidence: duloxetine: MD -2.70, 95% CI -5.03, -0.37; vortioxetine: MD 0.60, 95% CI -2.52, 3.72; very low certainty evidence for comparisons between other antidepressants and placebo). There were "small and unimportant" differences between most antidepressants in reduction of depression symptoms (high- or moderate-certainty evidence). Results were similar across other outcomes of benefit. In most studies risk of self-harm or suicide was an exclusion criterion for the study. Proportions of suicide-related outcomes were low for most included studies and 95% confidence intervals were wide for all comparisons. The evidence is very uncertain about the effects of mirtazapine (OR 0.50, 95% CI 0.03, 8.04), duloxetine (OR 1.15, 95% CI 0.72, 1.82), vilazodone (OR 1.01, 95% CI 0.68, 1.48), desvenlafaxine (OR 0.94, 95% CI 0.59, 1.52), citalopram (OR 1.72, 95% CI 0.76, 3.87) or vortioxetine (OR 1.58, 95% CI 0.29, 8.60) on suicide-related outcomes compared with placebo. There is low certainty evidence that escitalopram may "at least slightly" reduce odds of suicide-related outcomes compared with placebo (OR 0.89, 95% CI 0.43, 1.84). There is low certainty evidence that fluoxetine (OR 1.27, 95% CI 0.87, 1.86), paroxetine (OR 1.81, 95% CI 0.85, 3.86), sertraline (OR 3.03, 95% CI 0.60, 15.22), and venlafaxine (OR 13.84, 95% CI 1.79, 106.90) may "at least slightly" increase odds of suicide-related outcomes compared with placebo. There is moderate certainty evidence that venlafaxine probably results in an "at least slightly" increased odds of suicide-related outcomes compared with desvenlafaxine (OR 0.07, 95% CI 0.01, 0.56) and escitalopram (OR 0.06, 95% CI 0.01, 0.56). There was very low certainty evidence regarding other comparisons between antidepressants. Authors' conclusions: Overall, methodological shortcomings of the randomised trials make it difficult to interpret the findings with regard to the efficacy and safety of newer antidepressant medications. Findings suggest that most newer antidepressants may reduce depression symptoms in a small and unimportant way compared with placebo. Furthermore, there are likely to be small and unimportant differences in the reduction of depression symptoms between the majority of antidepressants. However, our findings reflect the average effects of the antidepressants, and given depression is a heterogeneous condition, some individuals may experience a greater response. Guideline developers and others making recommendations might therefore consider whether a recommendation for the use of newer generation antidepressants is warranted for some individuals in some circumstances. Our findings suggest sertraline, escitalopram, duloxetine, as well as fluoxetine (which is currently the only treatment recommended for first-line prescribing) could be considered as a first option. Children and adolescents considered at risk of suicide were frequently excluded from trials, so that we cannot be confident about the effects of these medications for these individuals. If an antidepressant is being considered for an individual, this should be done in consultation with the child/adolescent and their family/caregivers and it remains critical to ensure close monitoring of treatment effects and suicide-related outcomes (combined suicidal ideation and suicide attempt) in those treated with newer generation antidepressants, given findings that some of these medications may be associated with greater odds of these events. Consideration of psychotherapy, particularly cognitive behavioural therapy, as per guideline recommendations, remains important.