Clinical trials

The Cuidar-ME program is a web-based cognitive-behavioral intervention designed to promote well-being and mental health in women during (peri)menopause. The main goal of this research is to evaluate its acceptability, feasibility and preliminary evidence of efficacy of the intervention. This pilot randomized controlled trial uses a two-arm design and serves as a preliminary step before a full-scale RCT. A sample of at least 150 (peri)menopausal women, aged 40 to 60, will be recruited online. Participants who meet the eligibility criteria will be randomly assigned to either the web-based intervention (Cuidar-ME) or a waitlist control condition (which will receive access to the program after the study concludes). Participation in this study will last approximately 3 months. Participants in both conditions will be invited by the researchers via email to complete baseline and post-intervention assessments. These assessments will include self-report questionnaires evaluating several outcomes (e.g., quality of life, menopausal symptoms, depressive and anxiety symptoms, menopause representations, etc.), potential mechanisms of treatment response (emotional regulation and self-compassion), as well as user acceptability and feasibility.

This study will explore a new way for older adults to become more physically active. As people get older, it's common to gain weight and lose muscle strength. This combination can make it harder to do daily activities, increase the risk of falls, and impact overall quality of life. While we know that regular exercise is very beneficial, many older adults find it difficult to stick to traditional exercise programs due to lack of time, motivation, or energy. This research project, called COMPASS 65+, will test an innovative approach called "snack exercise." Instead of one long workout, "snack exercise" involves doing several short bouts of activity, a few minutes at a time, throughout the day. The main idea is that these short, frequent bouts of activity might be easier to fit into a daily routine and less tiring than longer exercise sessions. The purpose of this study is to see if a "snack exercise" program is a feasible and enjoyable way for adults aged 65 and over, who are overweight or obese, to improve their health. The study will be conducted in two main parts. First, the research team will talk with older adults to understand what helps or hinders them from being active to co-design the program. Second, volunteers will be randomly assigned to either a "snack exercise" group or a control group. Participants in the "snack exercise" group will attend sessions that combine theory and practice to learn how to perform these exercises and will receive individualized prescriptions to perform the "snacks" (short bouts) at home. The control group will receive a brief educational counselling session on physical activity. Participants' health status, body composition, and physical fitness will be assessed at baseline, after the 12 weeks intervention, and again 6 weeks post-intervention to evaluate the maintenance of any improvements. These outcomes will help determine whether short bouts of 'exercise snacking' constitute a feasible and effective strategy to promote functional capacity, metabolic health, and long-term adherence to physical activity.

Dementia incidence is rising, posing a public health challenge, but 45% of cases can be prevented by addressing modifiable risk factors. Multidomain trials show that lifestyle changes can improve cognitive function and reduce dementia risk (like the FINGER trial). The REMINDER program, a Portuguese-based dementia risk reduction protocol, was developed for community-dwelling older adults aged 55 and above. However, older adults in Residential and Daycare Facilities (RDF) have distinct needs that demand program adaptation to ensure its relevance and effectiveness. In addition, more studies are needed to evaluate the impact of multidomain interventions with older adults in RDF. To address these challenges, the REMINDER4Care program was developed as a tailored, multidomain intervention to reduce dementia risk. It emphasizes social and cognitive engagement and advances its adaptation and evaluation in Residential and Daycare Facilities (RDF). To assess efficacy, the investigators will perform a Randomized Controlled Trial.

The development of post-adoption interventions aimed at promoting parental well-being and positive parenting is an urgent need. Mindful Parenting-based interventions appear to be particularly promising in this field, as they address parents' needs in coping with the emotional challenges of parenting and seem to foster greater compassionate, non-judgmental acceptance toward themselves and their children, as well as enhance the self-regulation of immediate emotional states in favor of long-term goals that support the parent-child relationship. However, the delivery of such interventions in face-to-face formats for adoptive parents (APs), particularly within the scope of universal prevention, faces considerable barriers (e.g., wide geographical dispersion of APs, limited mental health specialization among adoption service teams). eHealth tools represent an innovative pathway for intervention that may help overcome these barriers, given their multiple advantages, including: (1) improved access to healthcare regardless of time and location, (2) greater user autonomy in managing their own care, and (3) enhanced quality and innovation in service delivery, supported by the diversity, efficiency, and technological advancement of these systems. The primary goal of this study is to evaluate the effectiveness of AdoptMindful2Care@Web, a new 9-module, web-based post-adoption psychological intervention grounded in the principles of mindful parenting. This pilot randomized controlled trial, with a two-arm design, precedes the full RCT planned as AdoptMindful2Care@Web. It is open to mothers and fathers who have at least one adoptive child under 18 years of age, whose adoption was legally decreed by the court less than 24 months prior to enrollment, who are not involved in any other ongoing adoption process, who are able to read and write in Portuguese, and who have regular access to the internet and electronic devices. A minimum of 90 families will be recruited with the support of all Portuguese governmental adoption agencies. After expressing interest in participating through an expression-of-interest form available on the project website, a member of the research team will contact them by telephone to conduct an initial screening (brief interview), with the following aims: (1) to clarify any questions regarding the study and (2) to assess their eligibility for participation (i.e., to confirm whether they meet the inclusion criteria and do not fall under any exclusion criteria). At the end of the telephone screening, they will be informed of the decision of eligibility. If deemed eligible and willing to participate, a specific date and time will be scheduled for completion of the online study assessment protocol corresponding to the first assessment point (T0). To support adherence to this appointment, a reminder will be sent on the scheduled day (via text message or email, as applicable). Eligible participants will be randomly assigned to either the intervention group (AdoptMindful2Care@Web) or a waitlist control group (participants will receive the intervention after the study concludes). The intervention includes eight core modules plus a follow-up module, all carried out via an online platform, each lasting approximately 40 minutes. Participants in both groups will complete assessments at four time points: baseline, post-intervention, 1- and 2-month follow-up. These assessments will include both self-report (e.g., parenting stress) and hetero-report measures (e.g., children's emotional and developmental difficulties).

The goal of this clinical trial is to learn whether PSYCHOPATHY.COMP, an individual compassion-focused, therapy-based intervention of 20 weekly sessions, can reduce psychopathy in prison inmates. Psychopathy is linked with the most severe and persistent forms of antisocial behavior. This trial will also learn whether the program improves emotional and behavioral regulation. The main questions are: * Does PSYCHOPATHY.COMP reduce psychopathy? * Does PSYCHOPATHY.COMP improve emotional and behavioral regulation? Researchers will compare PSYCHOPATHY.COMP with the usual individual case management support provided in prisons. Portuguese-speaking adult male prison inmates will be invited to participate. Those who consent to participate will be screened for inclusion (T0). A total of 200 eligible participants will take part. All participants will be invited to complete a baseline assessment (T1, pre-treatment assessment), after which they will be randomly assigned to receive PSYCHOPATHY.COMP or the usual care provided in the prison for a period of around six months. All participants will be invited to complete a post-treatment assessment (T2) and a six-month follow-up assessment post-treatment. Assessments will collect data on sociodemographic characteristics and legal/criminal information, psychological outcomes (psychopathy, emotional regulation, and behavioral regulation), psychological mediators (mechanisms of change: compassion-related variables), and moderators (personality pathology), and data on social desirability. This study aims to contribute to advancing scientific knowledge about whether and how to reduce psychopathy among prison inmates and have an impact on clinical practice and society by making available evidence-based interventions to this at-risk/high-risk population.

Firefighters are routinely exposed to potentially traumatic events, making them vulnerable to debilitating mental health problems. Consequently, promoting well-being and the ability to respond effectively and safely to work demands are vital. The FIRE is an innovative mindfulness, Acceptance and Commitment Therapy, and compassion-based manualized intervention encompassing eight weekly group sessions delivered at Fire Stations. A preliminary version of this program will be refined based on qualitative inputs from structured interviews with firefighters and emergency/civil protection sector stakeholders. The FIRE feasibility dimensions of adaptation, acceptability, implementation, practicality, integration, and limited efficacy will be evaluated in a two-arm, 1:1, non-blinded randomised controlled trial. The extent to which the FIRE contributes to the promotion of well-being and the decrease of psychopathological symptoms, and the causal theory underlying FIRE, will be explored through an examination of potential mechanisms of change.

Social functioning, fundamental to adolescent's development and mental health, may be impaired by polarizing problematic social functioning, namely externalizing symptoms manifested by Oppositional Defiant Disorder and internalizing symptoms portrayed by Social Anxiety Disorder. Despite their high prevalence and similar associated impairments, interventions targeting these disorders are differently conceived. Alternatively, Acceptance and Commitment Therapy (ACT) proposes that those apparently dissimilar social difficulties are rooted in similar processes. Though research has shown ACTs' efficacy in changing adults' internalizing and externalizing symptoms, studies on the potential of ACT in changing those problematics in adolescence are still scarce. This project proposes to conduct three clinical trials to test the efficacy and (dis)similarities of an transdiagnostic ACT intervention for changing internalizing and externalizing symptomatology in adolescents. It will amplify the transdiagnostic and evidence-based application of ACT to adolescents presenting polarizing disorders in the social functioning spectrum.

Diet is established among the most relevant adjustable variables of human health in modern societies. The recognition by the World Health Organization of cognitive impairment and dementia associated with aging as one of the major public health challenges of our time, highlights the imperative need for a more comprehensive understanding of how different aspects of lifestyle, in particular diet, affect neural function and consequent cognitive performance throughout lifespan. The brain is endowed with fine mechanisms for a precise spatial and temporal control of cerebral blood flow (CBF) according to neural activity, the neurovascular coupling (NVC). Mounting evidence from preclinical and human studies demonstrate that NVC dysfunction is a key early factor contributing to the pathogenesis of cognitive decline and vascular cognitive impairment (VCI) in aging and conditions associated with accelerated microvascular aging, such as cerebral small vessel disease (cSVD). Failure at any part of the NVC pathway disrupts CBF resulting in catastrophic depletion of oxygenation and energy supply to brain cells, and, in the long run, to neuronal dysfunction and cognitive impairment. The investigators have shown that nitric oxide (NO) synthesized by neuronal nitric oxide synthase (nNOS) is a direct mediator of NVC and that decreased bioavailability of NO along aging compromised NVC and reduced local CBF. Shortly after the identification of nNOS as a source of NO for vasodilation in the brain, an alternative pathway for NO production independent of nNOS, relying on the sequential reduction of nitrate, the nitrate:nitrite:NO pathway, was unveiled. Nitrate consumed in green leafy vegetables as part of a normal diet is bioactivated to nitrite and both compounds are permanent constituents of blood/tissues in animal species, influencing CBF and resulting in improvements in learning and memory in rodents and VCI patients. However, a critical question remains on whether NO produced from nitrite is functionally linked to neuronal activation. This is key to understanding whether dietary nitrate can be linked to neuronal-dependent CBF increases and cognitive performance. The investigators and others have shown that upon excitatory stimulation, ascorbate is released from neurons being available for nitrite reduction and our preliminary data supports that NO bioavailability and CBF might be maintained independently of nNOS by the reduction of nitrite to NO in the brain extracellular space upon neuronal activation (unpublish data). This innovative mechanism functionally links the production of NO from nitrite to neuronal activation, triggering CBF increases and maintaining an operative NVC. A further facet is that, bridging diet and cognitive performance, this mechanism incorporates modulatory elements which is open to adjustment by diet via nitrate. Thus, in this pilot trial a proof of concept study will be conducted to investigate the clinical impact of a dietary nitrate supplementation intervention in a clinical population with VCI due to small vessel disease, as measured by changes on NVC and cognitive performance. The investigators hypothesise that functional NVC is maintained operative in VCI patients by increasing NO bioavailability in the extracellular space of the brain through a nitrate -rich diet that, in turn, supports an adequate CBF in response to neuronal activation, modulating the molecular mechanisms and cognitive performance of disease-related physiological and cognitive markers.

Parkinson's disease (PD) has a substantial impact on daily life and significantly affects functioning, mental health and quality of life. Although considered a disease of the elderly, an early diagnosis is also common. Non-pharmacological interventions have been increasingly recommended for PD, including psychotherapy, with emerging evidence suggesting that Acceptance and Commitment Therapy (ACT) may be suitable to support individuals living with PD. This project aims to expand the current evidence for ACT interventions in this population by developing, implementing, and investigating the preliminary efficacy of a novel online-delivered ACT intervention (Empower your mind to embrace your life) for individuals with a diagnosis of young-onset PD. For this purpose, a feasibility study will be conducted to assess the acceptability and preliminary efficacy of the intervention across two groups (control and ACT intervention). This group-based intervention consists of eight weekly sessions and will be delivered in an online format (via videoconferencing). Outcome measurement will be assessed at pre-intervention, post-intervention, and at 3-month follow-up. When comparing changes in outcome variables between the control and intervention groups at post-treatment, improvements are expected only in the intervention group. These improvements are also expected to be maintained over time (at 3-month follow-up). Lastly, changes in psychological (in)flexibility processes are expected to predict changes in outcome variables in the intervention group. This study will provide important insights to research and clinical practice by providing data on the feasibility and preliminary efficacy of this novel ACT-based intervention for the context of young-onset PD.

Heart failure (HF) is a clinical syndrome with increasing incidence and prevalence, associated with high morbidity, mortality, and economic impact, despite therapeutic advances. Myocardial fibrosis is a common feature across different pathophysiological processes and plays a key role in HF development, with growing research interest specifically in non-ischemic dilated cardiomyopathy (HFrEF phenotype) and hypertrophic cardiomyopathy (HFpEF phenotype). Given its potential reversibility with certain drugs, fibrosis is an attractive therapeutic target, requiring non-invasive methods to monitor fibrogenesis and treatment efficacy. Cardiac magnetic resonance imaging (CMR) is the gold standard for detecting fibrosis but cannot distinguish between active and inactive fibrosis or detect early stages, limitations that may be addressed by gallium-68-labeled fibroblast activation protein inhibitor positron emission tomography/computed tomography (68Ga-FAPI PET/CT). This single-center, prospective, observational pilot study aims primarily to assess myocardial fibrosis in patients with HFrEF (non-ischemic dilated cardiomyopathy) and a subtype of HFpEF (hypertrophic cardiomyopathy) using 68Ga-FAPI PET/CT compared to CMR. Secondary objectives include developing 68Ga-FAPI uptake assessment methodologies for future anti-fibrotic therapy studies and correlating fibrosis with serum cardiac biomarkers and cardiovascular events.

Social cognition seems to develop atypically in autism, particularly in processes such as faces perception, joint attention and social information processing. In this sense, and using an Emotional Paradigm of Facial Expressions (EFP) with a Brain-Computer Interface (BCI) based on Electroencephalography (EEG), the investigators intend to evaluate its effectiveness as a medical device in Autism Spectrum Disorder (ASD), namely: improving 1) social skills and 2) reducing generalized anxiety, 3) improve error monitoring, and consequently verify 4) an increase in motivation. To this end, the investigators will test a gamified intervention (EFP), using personalized feedback in real time. In this gamified interface, there is an artificial agent that learns rules through Reinforcement Learning using the evoked potentials from the participant as they observe the agent's right or wrong actions. The hypothesis is that this approach allows, during the gamified task (EFP), not only the agent/interface to learn, but also the participant through operant conditioning and implicit scrutiny of errors, which makes it particularly interesting for disorders in which error monitoring processes are compromised, as in ASD.

This pilot randomised controlled trial aims to assess the feasibility, acceptability, and preliminary efficacy of an intervention program promoting Mental Health Literacy. A 10-week group treatment, 90 minutes each session, for adults and older adults with Chronic Pain. Half of the participants will receive the intervention immediately (experimental group), while the other half will not receive it initially. Still, they will receive it after the main phase of the study is completed (control group in waiting list). The intervention focuses on increasing Mental Health Literacy and reducing maladaptive beliefs and behaviours associated with pain. It also explores mechanisms and moderators of change.

Body Dysmorphic Disorder (BDD) is a severe psychiatric condition characterized by persistent and intrusive preoccupations with perceived flaws in physical appearance, which are typically unnoticeable or appear minor to others. BDD is associated with significant psychological distress, functional impairment, and reduced quality of life. Despite its prevalence and clinical severity, BDD remains frequently underdiagnosed and misdiagnosed. While Cognitive Behavioural Therapy (CBT) and Selective Serotonin Reuptake Inhibitors (SSRIs) are currently considered standard treatments, emerging evidence suggests that third-wave psychotherapies, such as Acceptance and Commitment Therapy (ACT) and Compassion-Focused Interventions, may offer additional benefits. This project aims to advance clinical care and scientific understanding of BDD by developing, implementing, and evaluating the preliminary efficacy of MIND-over-MIRROR-a novel group-based psychological intervention integrating ACT and compassion-based strategies for individuals exhibiting high levels of BDD symptomatology. The intervention consists of eight weekly sessions and one follow-up booster session, delivered in an online or hybrid format. A randomized feasibility study will be conducted to examine the intervention's acceptability, practicality, and preliminary clinical efficacy in adults aged 18 to 65 years. A multi-method assessment framework will be employed, with self-report measures collected at baseline, post-intervention, and 3-month follow-up. Additionally, participants from experimental and control groups will report on their weekly BDD symptomatology. Participants in the intervention group who consent will also undergo computerized behavioural tasks and functional neuroimaging using functional near-infrared spectroscopy (fNIRS) to explore neural and cognitive correlates of treatment outcomes. Improvements are expected in core clinical outcomes, including BDD symptom severity, and it is hypothesized that changes in targeted psychological processes (e.g., self-compassion) will mediate these effects. This study will contribute novel and clinically relevant data regarding the feasibility and potential effectiveness of contextual behavioural therapies for BDD, with implications for both research and practice.

According to the literature, the prevalence of anxiety, depression, and/or burnout symptoms among healthcare workers is high. There are several factors than can, directly or indirectly, be related to these symptoms, being the leadership styles one of them. Toxic leadership, as a form of malicious leadership, has been shown to negatively impact the mental health and wellbeing of the workforce, through the adoption of dysfunctional behaviour and/or the presence of deviant personality traits (psychopathic, Machiavellianism, narcissistic) in leaders. Despite its relevance, there is an absence of studies on the efficacy of intervention programs aimed to reduce the impact of toxic leadership styles in the workplace, namely among health care professionals. Compassion Focused Therapy (CFT) is considered an effective therapeutic approach for the rehabilitation of individuals with several psychopathological symptoms/disorders (e.g., anxiety, stress, burnout, and deviant personality traits) and for the establishment of healthy relationships with friends, family, and coworkers. In the workplace, CFT-based interventions have been shown to promote employees' wellbeing, through the reduction of stress and burnout symptoms and improvement of healthy and compassionate interpersonal relationships. It is thus mandatory to develop and test cost-effectiveness CFT-based intervention programs able to mitigate the impact of toxic leadership styles in the workforce, promoting compassionate workplaces in health care systems. To fulfil this gap, this clinical trial intends to develop and preliminarily test the efficacy of a short-term and low-time consuming internet delivery CFT-based intervention (iWork.COMP) specifically designed to mitigate the impact of toxic leadership styles through the development of compassionate motivation among health care professionals. Following a Randomized Controlled Trial, with 200 participants allocated to either a treatment group (TG) or a waiting-list control group (WLCG), it is hypothesized that the iWork.COMP will reduce the impact of toxic leadership styles, deviant traits and burnout symptoms among the TG when compared with the WLCG. Moreover, we expect that the iWork.COMP will promote wellbeing and a compassionate motivation among the TG when compared with the WLCG.

The goal of this clinical trial is to assess the efficacy of the Unified Protocol for the Transdiagnostic Treatment of Emotional Disorders for Adolescents (UP-A; Ehrenreich-May et al., 2018) as a universal school-based preventive intervention (UP-A Kind) in adolescents aged 11-18. This intervention aims to prevent emotional symptoms and improve adolescents' mental well-being in school setting, assessing changes in transdiagnostic processes. Researchers will compare an experimental group and a control group. Participants will participate in eight weekly sessions and will be assessed at 4 time points (pre- and post-treatment and 3-, 6- and 12-month follow-up). Control group participants will receive no intervention and will be assessed at the same time points.

This exploratory project aims to develop and pilot test, in a parallel group randomized controlled trial (RCT) design, the feasibility, acceptability, and preliminary efficacy of a self-management virtual reality (VR) 8-week program for pain management and mental health in patients with chronic post-stroke pain (CPSP), in two assessment moments (pre- to post-intervention).

t is recognized that cortisol, a hormone produced by the adrenal glands, is a marker that is elevated in patients with psychological disorders, particularly anxiety. On the other hand, Temporomandibular Disorders (TMD) are a condition with a multifactorial etiology, in which emotional disturbances play a crucial role. Therefore, the aim of this study is to evaluate whether patients with TMD have higher levels of salivary cortisol compared to the general population. Initially, an assessment will be conducted using the Diagnostic Criteria for Temporomandibular Disorders (DC/TMD) protocol to determine whether the patient suffer of any kind of Temporomandibular Disorder. Based on the results, individuals will be classified into two groups: the study group, consisting of patients with TMD, and the control group, composed of individuals without the disorder. Those who agree to participate will be required to sign an informed consent form. Subsequently, a saliva sample will be collected for analysis.

Temporomandibular disorder (TMD) refers to a group of musculoskeletal conditions that affect the temporomandibular joint (TMJ), the masticatory muscles, and the associated structures. It is assumed that 30 to 40% of cases of acute painful TMD becomes chronic. Chronic pain is a significant public health problem, affecting professional and social activities, emotional state, and quality of life. The pathophysiological mechanisms involved in chronic orofacial pain are complex and multifaceted and not yet fully understood. The coexistence of psychological factors associated with vast peripheral and central mechanisms makes chronic orofacial pain treatment a complex challenge. Due to the complexity of chronic TMDs, some patients remain refractory to current therapeutic methods. Thus, several efforts have been made to develop therapies aimed at the treatment of neuroplastic changes induced by chronic pain. In this sense, transcranial stimulation methods appear to be a promising technique. Transcranial Magnetic Stimulation (TMS) is a non-invasive, safe, and approved treatment for clinical use in psychiatric disorders such as depression and chronic pain. Given the above, it is necessary to develop studies to investigate the TMS effectiveness in chronic TMD. This study aims to evaluate the effectiveness of transcranial magnetic stimulation in patients with chronic temporomandibular disorders. An additional objective is to determine possible predictors for treatment success based on the assessment of functional brain connectivity and psychosocial characteristics.

This study aims to evaluate the effectiveness of a complementary therapy using Yoga within the scope of First Health Care in Portugal, in pain control, quality of life and well-being of the patients with Fibromyalgia. It also, pretends to assess the viability and to identify the barriers to this sort of therapy in the context of Primary Health Care.

The Mind programme for cancer patients was developed by this project PI through the integration of ACT, mindfulness and CFT components specifically adapted to the needs of a cancer population. This intervention aims at improving well-being, preventing subsequent distress, and promoting adaptation to the disease and posttreatment period. A recent pilot study presented preliminary findings on this intervention, suggesting high acceptability and efficacy in improving self-reported psychological health in breast cancer patients undergoing Radiotherapy treatment. Nevertheless, this study's small sample size, methodology (inactive control group), and exclusive reliance on self-reported data limit the interpretation and generalization of results, creating an avenue for the optimization and further testing of the programme through more robust and reliable methods. The aim of this project is therefore to optimize the Mind programme taking into consideration the results from its pilot study and to conduct a Randomized Controlled Trial on the efficacy of the intervention in improving not only mental health outcomes but also biological markers, as well as on its cost-effectiveness, in women with breast cancer. The superiority of the Mind programme will be compared to a support group intervention through the analysis of changes in cancer-specific quality of life, depressive symptoms and anxiety severity, psychological experiences, and immunological and epigenetics markers related to mental health and breast cancer prognosis. All participants will receive the intervention that shows better results.

This study aimed to evaluate the effectiveness of air polishing systems compared to the exclusive use of oral hygiene instruction in the treatment of peri-implant mucositis

Until now, neuropsychological interventions aimed to optimize cognitive function and to have functional impact in individuals at risk of AD (MCI patients) were scarce in validity studies. While some RCTs have been developed in cognitive training interventions, comparative studies of merged interventions (cognitive, social and behavioral stimulation) with adequate control groups are absent, diminishing the professionals' trust on the adoption of these interventions for supporting patients. As such, the present proposal will develop a validation trial testing a multicomponent neuropsychological intervention (REMINDER), based on personal development, cognitive compensatory aids, meaningful goals setting, and behavior change techniques. The investigators will analyze its short/long-term gains and AD conversion rates. By aiming to provide a good validation study for REMINDER, the investigators will examine neurobiological, neurocognitive and functional outcomes of this intervention in comparison with an active control group (psychoeducation) in order to foster an effective outcome assessment of an intervention for individuals at risk of AD.

Transdiagnostic approaches have been proposed as more truthfully representing mental health problems. Acceptance and Commitment Therapy (ACT) is a transdiagnostic approach that proposes Psychological Inflexibility/Flexibility (PI/PF) as the root of human suffering/flourishing. ACT has been recognized as conceptually and clinically relevant for adult disorders. However, during adolescence, when anxiety disorders are highly prevalent, the same evidence is scarce. Specifically, methodologically robust designs investigating ACT's efficacy on adolescents' ADs are scarce and mechanisms underlying change during ACT for adolescents with ADs have not been investigated. Therefore, this study aims to adapt, implement, and investigate the efficacy of an online delivered (through videoconference) ACT intervention to adolescents presenting SAD or GAD, thus contributing to amplifying the transdiagnostic application of ACT to these disorders. A Randomized Controlled Trial (RCT) with 3 groups (i.e., Control, GAD intervention, and SAD intervention groups) of adolescents aged between 14 and 18 years old will be conducted. Outcome measurement will be assessed at pre-intervention, post-intervention, and at 3- and 6-month follow-ups. The investigators expect improvements in outcome variables (e.g., anxiety symptoms) at post-treatment for intervention groups. When comparing changes in outcome variables between the control and the intervention groups, improvements are expected only in the groups receiving intervention. Additionally, similar effects on outcome measures are expected in both intervention groups with gains being maintained over time (i.e., at 3- and 6-months follow-up). Finally, changes in PI/PF processes are expected to predict changes in outcome variables in both intervention groups. This RCT will provide valuable insights that can potentially enhance the efficacy of treatment modalities, contributing to improved well-being for adolescents with ADs.