Communication about hereditary cancer risk to offspring: A systematic review of children's perspective.

OBJECTIVE: The present review describes how children experience hereditary cancer risk communication within the family. METHODS: Searches for studies between 1990 and 2020 on PubMed and EBSCO were undertaken, and 15 studies met the inclusion criteria, following Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. The findings informed: (1) how, when and what is discussed about hereditary cancer risk in the family; (2) how does family communication about hereditary cancer risk impact children on psychosocial and behavioral outcomes; (3) what are the child's preferences regarding hereditary cancer risk communication within the family. RESULTS: Disclosure is done mostly by both parents, or mothers only, which is in accordance with the children's preferences. Children value open communication about cancer risk with their parents, although they report experiences of fear, surprise, feeling unhappy, and concern about the increased risk of cancer. Regardless of the method of disclosure, children may be particularly sensitive to their parent's emotional state at the time of disclosure, and they learn from their parents' experiences the potential implications of cancer risk. Children also report that it would be helpful to learn more about genetic cancer syndromes via written materials, and/or meet a genetic counselor. CONCLUSIONS: Children rely on their parents as the primary models of the hereditary cancer experience. Therefore, parents play a central role in the psychological adjustment of children. Findings point to the relevance of family-centered care in hereditary cancer risk that targets not only the mutation carrier individually but also their children and partners.

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.

Idiographic patient reported outcome measures (I-PROMs) for routine outcome monitoring in psychological therapies: Position paper.

Idiographic patient-reported outcome measures (I-PROMs) are a growing set of individualized tools for use in routine outcome monitoring (ROM) in psychological therapies. This paper presents a position statement on their conceptualization, use, and analysis, based on contemporary evidence and clinical practice. Four problem-based, and seven goal-based, I-PROMs, with some evidence of psychometric evaluation and use in psychotherapy, were identified. I-PROMs may be particularly valuable to the evaluation of psychological therapies because of their clinical utility and their alignment with a patient-centered approach. However, there are several challenges for I-PROMs: how to generate items in a robust manner, their measurement model, methods for establishing their reliability and validity, and the meaning of an aggregated I-PROM score. Based on the current state of the literature, we recommend that I-PROMs are used to complement nomothetic measures. Research recommendations are also made regarding the most appropriate methods for analyzing I-PROM data.

Problematic use of the internet during the COVID-19 pandemic: Good practices and mental health recommendations.

With the onset of the COVID-19 pandemic and the accelerated spread of the SARS-CoV-2 virus came jurisdictional limitations on mobility of citizens and distinct alterations in their daily routines. Confined to their homes, many people increased their overall internet use, with problematic use of the internet (PUI) becoming a potential reason for increased mental health concerns. Our narrative review summarizes information on the extent of PUI during the pandemic, by focusing on three types: online gaming, gambling and pornography viewing. We conclude by providing guidance for mental health professionals and those affected by PUI (with an outline of immediate research priorities and best therapeutic approaches), as well as for the general public (with an overview of safe and preventative practices).

Advances in problematic usage of the internet research - A narrative review by experts from the European network for problematic usage of the internet.

Global concern about problematic usage of the internet (PUI), and its public health and societal costs, continues to grow, sharpened in focus under the privations of the COVID-19 pandemic. This narrative review reports the expert opinions of members of the largest international network of researchers on PUI in the framework of the European Cooperation in Science and Technology (COST) Action (CA 16207), on the scientific progress made and the critical knowledge gaps remaining to be filled as the term of the Action reaches its conclusion. A key advance has been achieving consensus on the clinical definition of various forms of PUI. Based on the overarching public health principles of protecting individuals and the public from harm and promoting the highest attainable standard of health, the World Health Organisation has introduced several new structured diagnoses into the ICD-11, including gambling disorder, gaming disorder, compulsive sexual behaviour disorder, and other unspecified or specified disorders due to addictive behaviours, alongside naming online activity as a diagnostic specifier. These definitions provide for the first time a sound platform for developing systematic networked research into various forms of PUI at global scale. Progress has also been made in areas such as refining and simplifying some of the available assessment instruments, clarifying the underpinning brain-based and social determinants, and building more empirically based etiological models, as a basis for therapeutic intervention, alongside public engagement initiatives. However, important gaps in our knowledge remain to be tackled. Principal among these include a better understanding of the course and evolution of the PUI-related problems, across different age groups, genders and other specific vulnerable groups, reliable methods for early identification of individuals at risk (before PUI becomes disordered), efficacious preventative and therapeutic interventions and ethical health and social policy changes that adequately safeguard human digital rights. The paper concludes with recommendations for achievable research goals, based on longitudinal analysis of a large multinational cohort co-designed with public stakeholders.

Preventing problematic internet use during the COVID-19 pandemic: Consensus guidance.

As a response to the COVID-19 pandemic, many governments have introduced steps such as spatial distancing and "staying at home" to curb its spread and impact. The fear resulting from the disease, the 'lockdown' situation, high levels of uncertainty regarding the future, and financial insecurity raise the level of stress, anxiety, and depression experienced by people all around the world. Psychoactive substances and other reinforcing behaviors (e.g., gambling, video gaming, watching pornography) are often used to reduce stress and anxiety and/or to alleviate depressed mood. The tendency to use such substances and engage in such behaviors in an excessive manner as putative coping strategies in crises like the COVID-19 pandemic is considerable. Moreover, the importance of information and communications technology (ICT) is even higher in the present crisis than usual. ICT has been crucial in keeping parts of the economy going, allowing large groups of people to work and study from home, enhancing social connectedness, providing greatly needed entertainment, etc. Although for the vast majority ICT use is adaptive and should not be pathologized, a subgroup of vulnerable individuals are at risk of developing problematic usage patterns. The present consensus guidance discusses these risks and makes some practical recommendations that may help diminish them.

Engaging Children and Young People in Digital Mental Health Interventions: Systematic Review of Modes of Delivery, Facilitators, and Barriers.

BACKGROUND: There is a high prevalence of children and young people (CYP) experiencing mental health (MH) problems. Owing to accessibility, affordability, and scalability, an increasing number of digital health interventions (DHIs) have been developed and incorporated into MH treatment. Studies have shown the potential of DHIs to improve MH outcomes. However, the modes of delivery used to engage CYP in digital MH interventions may differ, with implications for the extent to which findings pertain to the level of engagement with the DHI. Knowledge of the various modalities could aid in the development of interventions that are acceptable and feasible. OBJECTIVE: This review aimed to (1) identify modes of delivery used in CYP digital MH interventions, (2) explore influencing factors to usage and implementation, and (3) investigate ways in which the interventions have been evaluated and whether CYP engage in DHIs. METHODS: A literature search was performed in the Cochrane Library, Excerpta Medica dataBASE (EMBASE), Medical Literature Analysis and Retrieval System Online (MEDLINE), and PsycINFO databases using 3 key concepts "child and adolescent mental health," "digital intervention," and "engagement." Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines were followed using rigorous inclusion criteria and screening by at least two reviewers. The selected articles were assessed for quality using the mixed methods appraisal tool, and data were extracted to address the review aims. Data aggregation and synthesis were conducted and presented as descriptive numerical summaries and a narrative synthesis, respectively. RESULTS: This study identified 6 modes of delivery from 83 articles and 71 interventions for engaging CYP: (1) websites, (2) games and computer-assisted programs, (3) apps, (4) robots and digital devices, (5) virtual reality, and (6) mobile text messaging. Overall, 2 themes emerged highlighting intervention-specific and person-specific barriers and facilitators to CYP's engagement. These themes encompassed factors such as suitability, usability, and acceptability of the DHIs and motivation, capability, and opportunity for the CYP using DHIs. The literature highlighted that CYP prefer DHIs with features such as videos, limited text, ability to personalize, ability to connect with others, and options to receive text message reminders. The findings of this review suggest a high average retention rate of 79% in studies involving various DHIs. CONCLUSIONS: The development of DHIs is increasing and may be of interest to CYP, particularly in the area of MH treatment. With continuous technological advancements, it is important to know which modalities may increase engagement and help CYP who are facing MH problems. This review identified the existing modalities and highlighted the influencing factors from the perspective of CYP. This knowledge provides information that can be used to design and evaluate new interventions and offers important theoretical insights into how and why CYP engage in DHIs.

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.

Taking Care of an Adolescent and Young Adult Cancer Survivor: A Systematic Review of the Impact of Cancer on Family Caregivers.

Research usually investigates adolescents and young adults (AYA) with cancer in combination with younger and older cancer patients and survivors. However, AYAs with cancer are a unique group, and their caregivers' experience may also differ from other caregivers of cancer survivors. This systematic review aims to understand the impact of a cancer diagnosis on family caregivers, comparing the experience of caregivers of AYA childhood cancer survivors (AYA CCS) and caregivers of AYA with cancer. Relevant studies were identified through PubMed, Scopus, and Web of Science databases, and their quality was assessed using the Joanna Briggs Institute's critical appraisal checklists. Sixteen studies (17 reports) met the inclusion criteria. Findings were synthesized separately for caregivers of AYA CCS and caregivers of AYA with cancer. Results showed that caregivers in both groups experienced high distress after the diagnosis. Partners of AYAs with cancer experienced diminished quality of life (QoL) and over half reported moderate to high fear of cancer recurrence (FCR). Findings indicated that cancer negatively impacts family caregivers, regardless of the patient's age at diagnosis. However, findings are heterogeneous, and most do not focus on QoL or FCR. More research is needed on the impact of cancer among these family caregivers.

Distress facing increased genetic risk of cancer: The role of social support and emotional suppression.

OBJECTIVES: Healthy individuals from hereditary cancer families undergoing genetic testing for cancer susceptibility (GTC) report more distress when they perceive their social support as low and suppress their emotions. This study aimed to explore how suppressing emotions and perceiving others as unsupportive are related with cancer-risk distress. METHODS: We performed a regression-based mediation analysis to assess if expressive suppression mediates or is mediated by perceived social support in the relation with cancer-risk distress. Participants were 125 healthy adults aged over 18 (M = 36.07, SD = 12.86), mostly female (72,4%), who undergone GTC to assess the presence of hereditary breast and ovarian cancer or Lynch syndromes. RESULTS: Controlling for age and gender, we found a moderate size indirect effect of social support on cancer-risk distress through expressive suppression (ß = -0.095) and a direct effect of expressive suppression on cancer-risk distress. CONCLUSIONS: When healthy individuals from hereditary cancer families perceive their social network as less responsive, they tend to not express their emotions, which relates to increased distress facing GTC. PRACTICE IMPLICATIONS: Practitioners may assess cancer-risk related distress before the GTC and offer distressed individuals interventions focused on changing emotion regulation strategies in a safe group context.

Emotion-focused therapy for fear of cancer recurrence: A hospital-based exploratory outcome study.

Fear of cancer recurrence (FCR) is a main concern for most cancer survivors and can bring significant distress impacting well-being and quality of life. Although other psychological approaches have been developed for dysfunctional FCR, based on previous research, emotion-focused therapy (EFT) might also be a relevant intervention for treating this concern. A total of 17 adults with a cancer diagnosis and presenting FCR among other cancer-related concerns were offered EFT, delivered in a regular practice in a cancer hospital (mean number of sessions = 13, range: 4-25). Outcome and process instruments were used to assess general psychological distress, client-generated outcome items, and helpful and hindering aspects of therapy. Significant pre-post outcome differences were found, both for client-generated (d = 1.53) and standard (d = .88) measures, with no cases of reliable deterioration, although most patients did not show clinically significant change by the end of therapy. The most frequent helpful in-session processes were client verbal expression of experience and work on parts of self; the most common immediate session impacts were positive feelings and self-realizations. EFT may be a useful alternative treatment for FCR. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

"I have always lived with the disease in the family": family adaptation to hereditary cancer-risk.

BACKGROUND: Hereditary cancer syndromes have been conceptualized as a family level process. The present study explores the complexity and challenges of family adaptation to the hereditary cancer syndrome, in the context of genetic counseling and long-term cancer risk management and follow-up surveillance. METHODS: We performed semi-structured interviews with 13 participants with one of the following hereditary cancer syndromes: Lynch Syndrome, Hereditary Diffuse Gastric Cancer Syndrome, Hereditary Breast and Ovarian Cancer Syndrome, or Familial Adenomatous Polyposis. The interview was developed through a participatory approach with the involvement of healthcare professionals and individuals with first-hand experience of living with the hereditary cancer syndromes. RESULTS: The family is the main source of information and emotional support to deal with hereditary cancer syndromes. Multiple individual adaptation processes and communal coping networks interact, influencing the emotional and health-related behavior of family members. This is affected and affects the family's communication and its' members reactions to disclosure, with consequent changes in relationships. CONCLUSIONS: The systemic interdependent dynamics of family adaptation calls for family-centered care of genetic cancer syndromes.

Family Adjustment to Hereditary Cancer Syndromes: A Systematic Review.

Hereditary cancer syndromes are inherited pathogenic genetic variants that significantly increase the risk of developing cancer. When individuals become aware of their increased probability of having cancer, the whole family is affected by this new reality and needs to adjust. However, adjustment to hereditary cancer syndromes has been mainly studied at an individual level, and research about familial adjustment remains dispersed and disorganized. To overcome this gap, this review aims to understand how families adjust to genetic testing and risk management, and to what extent the family's adjustment influences the psychological response and risk management behaviors of mutation carriers. We conducted searches on the PubMed/Med Line, PsycInfo, SCOPUS, and Google Scholar databases and used the Mixed Methods Appraisal Tool (MMAT-v2018) to assess the methodological quality of each selected study. Thirty studies met the inclusion criteria. Most results highlighted the interdependent nature of adjustment of pathogenic variant carriers and their families. The way carriers adjust to the syndrome is highly dependent on family functioning and related to how family members react to the new genetic information, particularly partners and siblings. Couples who share their worries and communicate openly about cancer risk present a better long-term adjustment than couples who use protective buffering (not talking about it to avoid disturbing the partner) or emotional distancing. Parents need help dealing with disclosing genetic information to their children. These findings reinforce the importance of adopting a family-centered approach in the context of genetic counseling and the necessity of involving family members in research.

Citizen Consultation on Problematic Usage of the Internet: Ethical Considerations and Empirical Insights From Six Countries.

Citizens and scientists can work together to improve the collective well-being, if citizens are inspired to help the advancement of science, and researchers motivated to listen to the voices of citizens. The benefits of such collaboration are increasingly recognized by both citizens and scientists, as reflected in the growing number of related publications and initiatives. This is especially relevant for emerging areas of research, where early involvement of citizens could help to envision, prioritize, and plan prospective studies. The Problematic Usage of the Internet (PUI) is one such area, which is fast becoming a public mental health concern. However, there remains a lack of clarity regarding the practical guidelines and ethical requirements for citizen involvement at the earliest stages of PUI. In our paper, we propose a conceptual framework and a template for initial involvement of citizens in PUI. They are derived from our community case studies, conducted in six European countries (Georgia, Greece, Malta, North Macedonia, Portugal, and Spain) and consisting of consultation with diverse groups of interested citizens (students, parents, teachers, and health professionals). Informed by our consultation exercises, we also highlight four ethical aspects for citizen involvement in the research on PUI or novel disciplines in general. They follow simple guiding principles to ensure that scientists will: enable a long-term commitment and inclusive opportunities for citizens, challenge established power hierarchies, and support collaboration, co-production and co-authorship with citizens. We believe that the proposed practical guidelines and ethical considerations, provide a valuable foundation on which to advance our understanding and generate international strategies for citizen involvement in PUI.

Young People Who Meaningfully Improve Are More Likely to Mutually Agree to End Treatment.

Objective: Symptom improvement is often examined as an indicator of a good outcome of accessing mental health services. However, there is little evidence of whether symptom improvement is associated with other indicators of a good outcome, such as a mutual agreement to end treatment. The aim of this study was to examine whether young people accessing mental health services who meaningfully improved were more likely to mutually agree to end treatment. Methods: Multilevel multinomial regression analysis controlling for age, gender, ethnicity, and referral source was conducted on N = 8,995 episodes of care [Female = 5,469, 61%; meanAge = 13.66 (SD = 2.87) years] using anonymised administrative data from young people's mental health services. Results: Compared to young people with no change in mental health difficulties, those showing positive meaningful changes in mental health difficulties were less likely to have case closure due to non-mutual agreement (Odds Ratio or OR = 0.58, 95% Confidence Interval or CI = 0.50-0.61). Similarly, they were less likely to transfer (OR = 0.61, 95% CI = 0.49-0.74) or end treatment for other reasons (OR = 0.59, 95% CI = 0.50-0.70) than by case closure due to mutual agreement. Conclusion: The findings suggest that young people accessing mental health services whose symptoms meaningfully improve are more likely to mutually agree to end treatment, adding to the evidence that symptom improvement may be appropriate to examine as an indicator of a good outcome of accessing mental health services.

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.

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.

Theories of Change and Mediators of Psychotherapy Effectiveness in Adolescents With Externalising Behaviours: A Systematic Review.

BACKGROUND: Externalising behaviours are becoming a remarkably prevalent problem during adolescence, often precipitating both externalising and internalising disorders in later adulthood. Psychological treatments aim to increase the social functioning of adolescents in order for them to live a more balanced life and prevent these negative trajectories. However, little is known of the intervening variables and mediators involved in these treatments' change mechanisms. We conducted a systematic review, exploring the available evidence on mediators of psychological treatments for externalising behaviours and symptoms amongst adolescents (10 to 19 years old). METHODS: A systematic search was performed on Medline and PsycINFO databases, which identified studies from inception to February 23, 2020. Eligible studies included randomised controlled trials that enrolled adolescents with externalising symptoms and behaviours as, at least, one of the primary outcomes. A group of 20 reviewers from the COST-Action TREATme (CA16102) were divided into 10 pairs. Each pair independently screened studies for inclusion, extracted information from the included studies, and assessed the methodological quality of the included studies and the requirements for mediators, following Kazdin's criteria. Risk of bias of RCTs was assessed by the Mixed Methods Appraisal Tool. Extracted data from the included studies were reported using a narrative synthesis. RESULTS: Following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines (PRISMA), after removing duplicates, 3,660 articles were screened. Disagreements were resolved by consensus. In a second stage, 965 full-text articles were assessed for eligibility. A total of 14 studies fulfilled all inclusion criteria. The majority were related to systemic psychological treatment approaches. Two types of mediators were identified as potentially being involved in the mechanisms of change for better social improvements of adolescents: to increase healthier parent-adolescent relationships and parental discipline. However, there were significant and non-significant results amongst the same mediators, which led to discussing the results tentatively. CONCLUSIONS: Family variables were found to be the largest group of investigated mediators, followed by relational, behavioural, and emotional variables. No cognitive or treatment-specific mediators were identified. Both adequate behavioural control of adolescents' peer behaviour and a better positive balance in their relationships with their parents seemed to buffer the effects of externalising behaviours in adolescents. Several methodological limitations concerning mediation testing design, outcome measures, and mediator selection have been identified. ETHICS AND DISSEMINATION: Ethical approval was not required. PROSPERO registration number: CRD42021231835.

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.