"It takes time to see the whole picture": patients' views on improvement in cognitive behavioral therapy and psychodynamic therapy after three years.

Introduction: There is a lack of qualitative research that retrospectively explores how patients with major depressive disorder view their improvement in psychotherapy. Methods: Fifteen patients who received short-term cognitive behavioral therapy and psychodynamic therapy were individually interviewed approximately three years after completing therapy. Results: Some patients had altered their views on therapy, especially those who initially were uncertain of how helpful therapy had been. They said they did not realize the extent and importance of their improvement in therapy before some time had passed, which can be explained by the surprising cumulative effects of seemingly small changes. Discussion: This should make retrospective qualitative research an important part of future psychotherapy research.

Mediators of Outcome in Trauma-Focused Psychotherapy with Youth: A Systematic Review.

This article aimed to provide a systematic narrative synthesis of existing studies on the mediators of change in psychotherapy with adolescents (10-19 years) and transition age youth (TAY) (20-29 years) who have experienced trauma-related symptoms or posttraumatic disorder. Additionally, we were interested in identifying psychotherapy-, trauma type-, and clients' age- and gender-specific mediators of treatment outcome. Following the preferred reporting items for systematic reviews and meta-analyses, a total of 3,723 studies published in PubMed and PsycINFO databases were screened against inclusion criteria, revealing 15 eligible studies. No studies with only TAY were found; therefore, all results were limited to therapy with adolescents. Cognitive mediators were tested in 66% of selected studies, followed by parents/family-related, mental-health-related, therapy-related, and behavioral mediators. Moderate evidence was found for posttraumatic cognitions, whereas therapeutic alliance seemed to be a promising candidate for future research. Striking absence of non-cognitive-behavioral therapy interventions, emotional and adolescent-specific mediators, as well as studies with males and in non-Western societies was evident. Future original studies would benefit from applying methodological rigor in respect to mediation testing.

Mediators of outcome in adolescent psychotherapy and their implications for theories and mechanisms of change: a systematic review.

Psychotherapeutic treatment of adolescents requires age-specific approaches and thus plausibly also involves different change mechanisms than adult psychotherapy. To guide further research and improve therapeutic outcomes for adolescents, we reviewed all RCTs investigating mechanisms of change in the psychological treatment of adolescents to identify the most promising age-, disorder- or treatment-specific mediators. Following the preferred reporting items for systematic reviews (PRISMA), 106 studies were included that reported 252 statistical mediation tests assessed with 181 different measures. Most often studied and significant mediators were cognitive, followed by family-related, and behavioral variables. Several mediators were identified to be promising for future investigations: changes in negative thoughts, dysfunctional beliefs and metacognitive skills; family functioning and parenting skills; as well as successful engagement in therapy activities and increased impulse control. Symptom change during therapy was least often a mediator for other therapeutic changes. Relational and emotional mediators were largely understudied, whereas peer-influence appeared a promising mediator for intervention outcomes. Adolescence-specific mediators were most commonly investigated. Majority of studied mediators were not disorder-specific. There was a tendency to mainly test change mechanisms of specific theoretical models without considering other possible change theories. Further, virtually no studies fulfilled all criteria for rigorously investigating mediation and only nine were classified with an overall good study quality. While bearing in mind the current limitations in study designs, methodological rigor and reporting, there appears to be substantial evidence for transdiagnostic age-specific change models in the psychological treatment of adolescents. For future research, need for consensus on a core set of transdiagnostic and transtheoretical mediators and measures is highlighted. These should address likely core mechanisms of change, as well as take into account age-relevant developmental challenges and biological markers.

Examining Psychotherapeutic Processes with Depressed Adolescents: A Comparative Study of Two Psychodynamic Therapies.

To understand processes associated with better or poorer psychotherapy outcomes is vital. This study examined and contrasted interaction patterns between one therapist and two depressed 17-year-old girls, Johanna (good outcome) and Sonja (poor outcome), in short-term psychoanalytic therapies selected from an RCT. Outcome data were collected regarding level of inter- and intra-personal functioning and symptoms of depression. Process data were obtained using the Adolescent Psychotherapy Q-Set on all available sessions. Analyses yielded five relational patterns or "interaction structures" in the two therapy processes; Three explained most of the variance in sessions with Johanna (i.e., 'positive working alliance', 'therapist's active use of psychodynamic techniques', and 'a receptive patient') and two explained more of the variance in sessions with Sonja (i.e., 'therapist using a more problem-solving and symptom-oriented approach' and 'patient displaying limited capacity for mentalization'). The processes in the two cases presented differences related to mentalization, psychological mindedness, and attachment style of the patients. The therapist used different therapeutic approaches, favouring more psychodynamic interventions in the good outcome case and a more problem-solving and symptom-oriented approach with the poor outcome case. In the latter case, the relationship seemed to be more of a struggle.

Inter-Rater Reliability of the Structured Interview of DSM-IV Personality (SIDP-IV) in an Adolescent Outpatient Population.

Personality disorders (PDs) are a class of mental disorders which are associated with subjective distress, decreased quality of life and broad functional impairment. The presence of one or several PDs may also complicate the course and treatment of symptom disorders such as anxiety and depression. Accurate and reliable means of diagnosing personality disorders are thus crucial to ensuring efficient treatment planning and resource allocation, a fact which is widely acknowledged within the adult mental health field. In adolescents, on the other hand, the consensus view has been that the rapid and discontinuous processes of normal personality development render the construct of PD in adolescents clinically unhelpful and conceptually dubious. However, recent research has established the reliability and validity of the construct, heralding an increased interest in the field, with important conceptual and clinical implications. The present article presents reliability data for the Structured Interview of DSM-IV Personality (SIDP-IV) in an adolescent outpatient population. For this study, 25 interviews conducted by experienced clinicians were blindly re-scored based on sound recordings, which allowed for the calculation of intra-class correlation metrics. The intra-class correlation coefficient for categorical diagnosis of specific personality disorders was found to be 0.876 (95% CI 0.718-0.945); Cohen's kappa for presence/absence of personality diagnosis was found to be 0.896. The present study found excellent intra-rater reliability for the sample, which suggests that the SIDP-IV is a suitable instrument for assessing personality pathology in adolescent populations.

Personality Disorders as a Possible Moderator of the Effects of Relational Interventions in Short-Term Psychoanalytic Psychotherapy with Depressed Adolescents.

A significant proportion of adolescents suffering from major depressive disorder (MDD) are likely to have a co-morbid personality disorder (PD). Short-term psychoanalytic psychotherapy (STPP) was found to be one treatment of choice for adolescents suffering from MDD. BACKGROUND: The first experimental study of transference work-in teenagers (FEST-IT) demonstrated the efficaciousness of transference work in STPP with adolescents suffering from MDD. The usefulness of STPP may be enhanced by exploring possible moderators. METHODS: Depressed adolescents (N = 69), aged 16-18 years, were diagnosed with the structured interview for DSM-IV PDs and randomized to 28 weeks of STPP with or without transference work. A mixed linear model was applied. The moderator effect was investigated by a three-way interaction including "time", "treatment group" and "number of PD criteria". RESULTS: A small but significant moderator effect was found for cluster B personality pathology. Patients with a higher number of cluster B PD criteria at baseline did better up to one-year post-treatment where therapists encouraged patients to explore the patient-therapist relationship in the here and now. CONCLUSION: When treated with psychoanalytic psychotherapy for MDD, adolescents with cluster B PD symptoms seem to profit more from transference work than adolescents without such pathology.

Subjective well-being among psychotherapists during the coronavirus disease pandemic: A cross-cultural survey from 12 european countries.

OBJECTIVE: The aim of this study is to examine the amount of the total variance of the subjective well-being (SWB) of psychotherapists from 12 European countries explained by between-country vs. between-person differences regarding its cognitive (life satisfaction) and affective components (positive affect [PA] and negative affect [NA]). Second, we explored a link between the SWB and their personal (self-efficacy) and social resources (social support) after controlling for sociodemographics, work characteristics, and COVID-19-related distress. METHODS: In total, 2915 psychotherapists from 12 countries (Austria, Bulgaria, Cyprus, Finland, Great Britain, Serbia, Spain, Norway, Poland, Romania, Sweden, and Switzerland) participated in this study. The participants completed the Satisfaction with Life Scale (SWLS), the International Positive and Negative Affect Schedule Short Form (I-PANAS-SF), the General Self-Efficacy Scale, and the Multidimensional Scale of Perceived Social Support. RESULTS: Cognitive well-being (CWB; satisfaction with life) was a more country-dependent component of SWB than affective well-being (AWB). Consequently, at the individual level, significant correlates were found only for AWB but not for CWB. Higher AWB was linked to being female, older age, higher weekly workload, and lower COVID-19-related distress. Self-efficacy and social support explained AWB only, including their main effects and the moderating effect of self-efficacy. CONCLUSIONS: The results highlight more individual characteristics of AWB compared to CWB, with a more critical role of low self-efficacy for the link between social support and PA rather than NA. This finding suggests the need for greater self-care among psychotherapists regarding their AWB and the more complex conditions underlying their CWB.

Burnout among psychotherapists: a cross-cultural value survey among 12 European countries during the coronavirus disease pandemic.

The aim of this study was to examine cross-cultural differences, as operationalized by Schwartz's refined theory of basic values, in burnout levels among psychotherapists from 12 European countries during the coronavirus disease (COVID-19) pandemic. We focused on the multilevel approach to investigate if individual- and country-aggregated level values could explain differences in burnout intensity after controlling for sociodemographic, work-related characteristics and COVID-19-related distress among participants. 2915 psychotherapists from 12 countries (Austria, Bulgaria, Cyprus, Finland, Great Britain, Serbia, Spain, Norway, Poland, Romania, Sweden, and Switzerland) participated in this study. The participants completed the Maslach Burnout Inventory-Human Service Survey, the revised version of the Portrait Values Questionnaire, and a survey questionnaire on sociodemographic, work-related factors and the COVID-19 related distress. In general, the lowest mean level of burnout was noted for Romania, whereas the highest mean burnout intensity was reported for Cyprus. Multilevel analysis revealed that burnout at the individual level was negatively related to self-transcendence and openness-to-change but positively related to self-enhancement and conservation values. However, no significant effects on any values were observed at the country level. Male sex, younger age, being single, and reporting higher COVID-19-related distress were significant burnout correlates. Burnout among psychotherapists may be a transcultural phenomenon, where individual differences among psychotherapists are likely to be more important than differences between the countries of their practice. This finding enriches the discussion on training in psychotherapy in an international context and draws attention to the neglected issue of mental health among psychotherapists in the context of their professional functioning.

Therapists' Emotional Responses in Individual Therapy with Depressed Adolescents: An Evaluation of the Data Structure of the Feeling-Word Checklist-28.

Countertransference (CT) responses during therapy sessions can be understood as the therapist's emotional reactions towards the patient. Within adolescents' psychotherapy, little is known about the effects of the therapists' feelings on treatment outcome. The Feeling-Word Checklist-28 (FWC-28) is a self-report questionnaire designed to evaluate the therapist's in-session feelings during therapy with younger patients. The aim of the study was to evaluate the psychometric properties of the clinician-rated FWC-28 and explore the associations between the CT-subscales and therapeutic alliance. Data were collected from a randomized controlled trial in which 11 therapists specialized in child and adolescent psychotherapy treated 16- to 18-year-old patients (n = 62) with major depressive disorder in outpatient clinics. The patients received psychodynamic psychotherapy treatment over 28 sessions. Therapists rated their emotional responses towards their patients on FWC-28 after sessions 3, 12, 20, and 28. Principal component analysis (PCA) with oblique rotation was performed to find clinically meaningful subscales of the FWC-28. PCA revealed four clinically meaningful components termed as follows: inadequate, confident, motherly, and disengaged. The psychometric properties of the FWC and the reliability of the CT subscales measured with Cronbach's alpha were acceptable. The therapist-reported alliance showed significant and clinically meaningful correlations with all CT-subscales. Our findings indicate that the checklist is adequate for clinical practice and countertransference research in adolescents' psychotherapy.

Therapist-guided internet-based psychodynamic therapy versus cognitive behavioural therapy for adolescent depression in Sweden: a randomised, clinical, non-inferiority trial.

BACKGROUND: Adolescent major depressive disorder (MDD) is highly prevalent and associated with lifelong adversity. Evidence-based treatments exist, but accessible treatment alternatives are needed. We aimed to compare internet-based psychodynamic therapy (IPDT) with an established evidence-based treatment (internet-based cognitive behavioural therapy [ICBT]) for the treatment of adolescents with depression. METHODS: In this randomised, clinical trial, we tested whether IPDT was non-inferior to ICBT in the treatment of adolescent MDD. Eligible participants were 15-19 years old, presenting with a primary diagnosis of MDD according to DSM-5. Participants were recruited nationwide in Sweden through advertisements on social media, as well as contacts with junior and senior high schools, youth associations, social workers, and health-care providers. Adolescents who scored 9 or higher on the Quick Inventory of Depressive Symptomatology for Adolescents (QIDS-A17-SR) in an initial online screening were contacted by telephone for a diagnostic assessment using the Mini International Neuropsychiatric Interview. Participants were randomly assigned to ICBT or IPDT. Both interventions comprised eight self-help modules delivered over 10 weeks on a secure online platform. The primary outcome was change in depression severity measured weekly by the QIDS-A17-SR. Primary analyses were based on an intention-to-treat sample including all participants randomly assigned. A non-inferiority margin of Cohen's d=0·30 was predefined. The study is registered at ISRCTN, ISRCTN12552584. FINDINGS: Between Aug 19, 2019, and Oct 7, 2020, 996 young people completed screening; 516 (52%) were contacted for a diagnostic interview. 272 participants were eligible and randomly assigned to ICBT (n=136) or IPDT (n=136). In the ICBT group, 51 (38%) of 136 participants were classified as remitted, and 54 (40%) of 136 participants were classified as remitted in the IPDT group. Within-group effects were large (ICBT: within-group d=1·75, 95% CI 1·49 to 2·01; IPDT: within-group d=1·93, 1·67 to 2·20; both p<0·0001). No statistically significant treatment difference was found in the intention-to-treat analysis. Non-inferiority for IPDT was shown for the estimated change in depression during treatment (d=-0·18, 90% CI -0·49 to 0·13; p=0·34). All secondary outcomes showed non-significant between-group differences. INTERPRETATION: IPDT was non-inferior to ICBT in terms of change in depression for the treatment of adolescents with MDD. This finding increases the range of accessible and effective treatment alternatives for adolescents with depression. FUNDING: Kavli trust.

Parental Bonding and Relationships with Friends and Siblings in Adolescents with Depression.

According to attachment theory, the quality of the early child-parent bond determines the child's interpersonal relationships later in life. Utilising data from The First Experimental Study of Transference Work-In Teenagers (FEST-IT), the current paper investigated the connection between the self-reported quality of bonding with mother and father and the self-reported importance of relationships with friends and siblings in adolescents with depression. The scales employed were the Parental Bonding Instrument (PBI) and the Adolescent Relationship scale (ARS). A Pearson's correlation tested the relationship between the reported levels of maternal and paternal care and control, and the reported importance of friendship and relationship with siblings. Results revealed a statistically significant negative correlation between high levels of maternal control and importance of friendship, and a statistically significant positive correlation between high levels of paternal care and importance of relationships with siblings. The results are in line with Bowlby's theory of attachment.

Psychological Interventions for Young People With Psychotic Disorders: A Systematic Review.

Background: Psychotic disorders are commonly accompanied by intense psychological burden, and psychological interventions are usually needed in order to reduce the symptoms and help in maintaining or improving the level of psychological and social functioning after the onset of psychosis. The evidence-base for treating young people at risk for psychosis and adults with psychotic disorders is accumulating. Yet, pervasive systematic literature reviews that would include patients from the full age range being the most essential period for the risk of developing a psychotic disorder, a wide range of psychological interventions, and various types of clinical trials, have been lacking. The aim of this systematic review is to fill the gap by presenting the current research evidence from clinical trials on the effectiveness of psychological interventions for treating young people (12-30) with psychotic disorders. Methods: A systematic search was conducted in PubMed and PsycINFO followed by a 3-step screening process based on the PICOS strategy. Risk of bias of the included studies was assessed by the Mixed Methods Appraisal Tool (MMAT). Extracted data from the included studies is reported using a narrative synthesis. Results: Of the 1,449 publications screened, 40 from 25 studies were included in the review. Of these, 10 studies reported results from cognitive or behavioral therapy, nine from cognitive remediation therapy (CRT), and six from other types of therapies (i.e., integrative interventions combining psychoeducation and family/group interventions). All but one study found the target interventions to be effective, but the results mostly did not differ significantly from the control conditions in reducing symptoms and improving functioning, preventing relapses and hospitalization, or improving psychological or family variables. The most consistent findings were from CRT, showing more improvement in cognitive functioning compared to control conditions while not being superior in reducing symptom severity. Integrative interventions might be effective in treating young people suffering from psychotic disorders. Conclusion: There is some evidence that psychological interventions are effective for young people with psychotic disorders. However, with regard to symptom severity, psychotherapy does not outperform control conditions, and the results do not strongly favor any specific type of treatment. Systematic Review Registration: [https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42020166756], identifier [CRD42020166756].

Do Sleep Disturbances Improve Following Psychoanalytic Psychotherapy for Adolescent Depression?

Sleep disturbance is often a prominent symptom in adolescents diagnosed with major depressive disorder (MDD). Recent evidence indicates that short-term psychoanalytic psychotherapy (STPP) for depression may have an effect in reducing co-occurring sleep disturbance in youth. It is unknown if transference work (exploration of the patient-therapist relationship) has an additional effect in reducing sleep disturbance. Adolescents aged 16-18 years (n = 69, 84% female) who met diagnostic criteria for MDD based on the Mini International Neuropsychiatric Interview (M.I.N.I) were randomized to either STPP with transference work or without. Sleep problems were assessed at baseline, therapy session 20 (20 weeks), post-treatment (28 weeks), and one-year follow-up (80 weeks) with the Symptom Checklist-90-R. At baseline, 69% of the adolescents exhibited moderately to extreme sleep difficulties. Sleep disturbance was significantly correlated to depression depth at session 20 and at follow-up. Symptoms of insomnia significantly decreased from baseline to the end of treatment. Treatment gains were maintained until follow-up. No differences in recovery of sleep disturbance were found between the two treatment groups. The findings suggest that sleep disturbance improves following STPP for depression, with or without transference work. Future research should assess those with residual symptoms by different sleep measures.

Psychotherapy Dropout: Using the Adolescent Psychotherapy Q-Set to Explore the Early In-Session Process of Short-Term Psychodynamic Psychotherapy.

Research suggests that short-term psychodynamic psychotherapy (STPP) is an effective treatment for depression in adolescence, yet treatment dropout is a major concern and what leads to dropout is poorly understood. Whilst studies have begun to explore the role of patient and therapist variables, there is a dearth of research on the actual therapy process and investigation of the interaction between patient and therapist. This study aims to address this paucity through the utilisation of the Adolescent Psychotherapy Q-set (APQ) to examine the early treatment period. The sample includes 69 adolescents aged 16-18 years with major depressive disorder receiving STPP as part of the First Experimental Study of Transference Work-in Teenagers (FEST-IT) trial. Of these, 21 were identified as dropouts and were compared to completers on pre-treatment patient characteristics, symptomatology, functioning, and working alliance. APQ ratings available for an early session from 16 of these drop out cases were analysed to explore the patient-therapist interaction structure. Results from the Q-factor analysis revealed three distinct interaction structures that explained 54.3% of the total variance. The first described a process of mutual trust and collaboration, the second was characterised by patient resistance and emotional detachment, the third by a mismatch and incongruence between therapist and adolescent. Comparison between the three revealed interesting differences which taken together provide further evidence that the reasons why adolescents drop out of therapy vary and are multidimensional in nature.

Patient and Public Involvement in Youth Mental Health Research: Protocol for a Systematic Review of Practices and Impact.

Various health settings have advocated for involving patients and members of the public (PPI) in research as a means to increase quality and relevance of the produced knowledge. However, youth PPI has been an understudied area. This protocol paper describes a new project that aims to summarize what is known about PPI with young people in mental health research. In line with the Preferred Reporting Items for Systematic reviews and Meta-Analyses Statement guidelines we will identify and appraise suitable articles and extract and synthesize relevant information including at least two reviewers at each stage of the process. Results will be presented in two systematic reviews that will describe (a) how youth PPI has been conducted (Review1) and (b) what impact youth PPI had on the subsequent research and on stakeholders (Review2). To our knowledge, this is the first set of reviews that uses a critical appraisal tool, which is co-developed with children and young people. Findings from this project will provide valuable insights and set out the key steps to adopting adequate PPI methods when involving children and young people in mental health research.

Mediators and Theories of Change in Psychotherapy for Young People With Personality Disorders: A Systematic Review Protocol.

Background: Personality disorders (PDs) are a severe health issue already prevalent among adolescents and young adults. Early detection and intervention offer the opportunity to reduce disease burden and chronicity of symptoms and to enhance long-term functional outcomes. While psychological treatments for PDs have been shown to be effective for young people, the mediators and specific change mechanisms of treatment are still unclear. Aim: As part of the "European Network of Individualized Psychotherapy Treatment of Young People with Mental Disorders" (TREATme), funded by the European Cooperation in Science and Technology (COST), we will conduct a systematic review to summarize the existing knowledge on mediators of treatment outcome and theories of change in psychotherapy for young people with personality disorders. In particular, we will evaluate whether mediators appear to be common or specific to particular age groups, treatment models, or outcome domains (e.g., psychosocial functioning, life quality, and adverse treatment effects). Method: We will follow the reporting guidelines of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement recommendations. Electronic databases (PubMed and PsycINFO) have been systematically searched for prospective, longitudinal, and case-control designs of psychological treatment studies, which examine mediators published in English. Participants will be young people between 10 and 30years of age who suffer from subclinical personality symptoms or have a personality disorder diagnosis and receive an intervention that aims at preventing, ameliorating, and/or treating psychological problems. Results: The results will be published in a peer-reviewed journal and at conference presentations and will be shared with relevant stakeholder groups. The data set will be made available to other research groups following recommendations of the open science initiative. Databases with the systematic search will be made openly available following open science initiatives. The review has been registered in PROSPERO (evaluation is pending, registration number ID 248959). Implications: This review will deliver a comprehensive overview on the empirical basis to contribute to the further development of psychological treatments for young people with personality disorders.

Predictors and moderators of outcome of psychotherapeutic interventions for mental disorders in adolescents and young adults: protocol for systematic reviews.

BACKGROUND: Adolescence and young adulthood is a risk period for the emergence of mental disorders. There is strong evidence that psychotherapeutic interventions are effective for most mental disorders. However, very little is known about which of the different psychotherapeutic treatment modalities are effective for whom. This large systematic review aims to address this critical gap within the literature on non-specific predictors and moderators of the outcomes of psychotherapeutic interventions among adolescents and young adults with mental disorders. METHODS: The protocol is being reported in accordance with the Preferred Reporting Items for Systematic Review and Meta-Analysis Protocols (PRISMA-P) Statement. PubMed and PsycINFO databases will be searched for randomized controlled and quasi-experimental/naturalistic clinical trials. Risk of bias of all included studies will be assessed by the Mixed Methods Appraisal Tool. The quality of predictor and moderator variables will be also assessed. A narrative synthesis will be conducted for all included studies. DISCUSSION: This systematic review will strengthen the evidence base on effective mental health interventions for young people, being the first to explore predictors and moderators of outcome of psychotherapeutic interventions for a wide range of mental disorders in young people. SYSTEMATIC REVIEW REGISTRATION: PROSPERO CRD42020166756 .

Mediators in Psychological Treatments for Anxiety and Depression in Adolescents and Young People: A Protocol of a Systematic Review.

INTRODUCTION: Anxiety and depressive disorders are a significant problem that starts in childhood or adolescence and should be addressed early to avoid chronic mental conditions. There is strong evidence to demonstrate that psychological treatments are effective for these disorders, however, little is known on mediators and mechanisms of change of psychological treatment in adolescents and young adults. Understanding the pathways through which psychological treatments operate will facilitate more effective treatments. AIM: We aim to conduct a systematic review, exploring the available evidence on mediators of psychological treatments for anxiety and depression in adolescents and young adults. METHODS: A systematic search has been performed on PubMed and PsycINFO databases to identify studies from inception to 23rd February 2020. Eligible studies include randomized controlled trials and trials (quasi-experimental) designs that have enrolled adolescents and young adults presenting with depression and/or anxiety and that have examined mediators of psychological treatments. A group of 20 reviewers from the COST-Action TREATme (CA16102) divided into 10 pairs independently screen studies for inclusion, extract information from the included studies, and assess the methodological quality of the included studies and the requirements for mediators. The methodological quality will be assessed by The Mixed Methods Appraisal Tool. Extracted data from the included studies will be collected and presented using a narrative approach. DISCUSSION: This systematic review will summarize and provide a comprehensive overview of the current evidence on mediators of psychological treatments for anxiety and depression for adolescents and young adults. Results will allow the identification of strategies to optimize intervention to enhance clinical outcomes. ETHICS AND DISSEMINATION: Ethics approval is not required. Findings from this systematic review will be published in a peer-reviewed journal and disseminated at conferences and meetings. PROSPERO registration number: CRD42021234641.