Mathias Harrer

• Master of Science
• Researcher at Technical University of Munich

Objective: Digital stress interventions could be helpful as an “indirect” treatment for depression, but it remains unclear for whom this is a viable option. In this study, we developed models predicting individualized benefits of a digital stress intervention on depressive symptoms at 6-month follow-up. Method: Data of N = 1,525 patients with depre...

The scientific output generated in psychology has surged in recent decades, including the number of studies investigating psychological treatments. To keep track of all this evidence, we developed the “Metapsy” meta-analytic research domain: a comprehensive system of open databases and tailored software that allows for rapid evidence generation. We...

This protocol outlines an individual participant data (IPD) analysis investigating the temporal dynamics of schizophrenia symptoms during antipsychotic treatment. Using harmonized data from six antipsychotic drug trials, we aim to examine weekly trajectories of Positive and Negative Syndrome Scale (PANSS) sub-scores over a 26-week period. Our aim i...

Introduction: About 30% of depressed patients suffer from a protracted course in which the disorder continues to cause significant burden despite treatment efforts. While originally developed for relapse prevention, Mindfulness-Based Cognitive Therapy (MBCT) has increasingly been investigated in depressed patients with such difficult-to-treat cours...

Background: Chronic and treatment-resistant depression (DTD) is difficult to manage, and while Mindfulness-Based Cognitive Therapy (MBCT) and Cognitive Behavioral Analysis System of Psychotherapy (CBASP) are recommended treatments, their potential negative effects-including deterioration, suicidality, and adverse events-are not well understood. Obj...

Although treatments for depression are effective, many patients do not respond. Many new innovations are currently being developed, claiming to substantially improve outcomes. We propose a new method to assess the strength of these innovations. Based on response rates of current treatments, we can estimate how many treatments are needed in total to...

Background: It remains unclear which individuals with subthreshold depression benefit most from psychological intervention, and what long-term effects this has on symptom deterioration, response and remission. Aims: To synthesise psychological intervention benefits in adults with subthreshold depression up to 2 years, and explore participant level...

Insomnia disorder is a significant public health issue, but the prevalence estimates vary widely. We performed a meta‐analysis aiming to pool prevalence rates in studies (1) carried out in the general population (2) using a true random sample (3) and using a diagnostic interview, DSM based self‐report questions, or a questionnaire with a cut‐off es...

Although CBT has been found to be effective in the treatment of eating disorders, it is not clear if there are differences between treatment formats. We conducted a network meta-analysis (NMA) of randomized trials of broadly defined CBT comparing individual, group, guided self-help (GSH) and unguided self-help (USH) with each other or with a contro...

Importance Cognitive behavior therapy (CBT) is a first-line treatment for most mental disorders. However, no meta-analytic study has yet integrated the results of randomized clinical trials on CBT across different disorders, using uniform methodologies and providing a complete overview of the field. Objective To examine the effect sizes of CBT for...

Aims The comparability between self-reports and clinician-rated scales for measuring depression following treatment has been a long-standing debate, with studies finding mixed results. While the use of self-reports in psychotherapy trials is very common, it has been widely assumed that these tools pose a validity threat when masking of participants...

Background: Psychological interventions are increasingly discussed as a method to prevent major depressive disorder (MDD) in adults who already experience subthreshold depressive symptoms. In this individual participant data metaanalysis, we quantify the effect of preventive interventions against control on MDD onset in this population, and explore...

Aims There is considerable evidence that waiting list (WL) control groups overestimate the effect sizes of psychotherapies for depression. It is not clear, however, what are the exact causes for this overestimation. We decided to conduct a meta-analytic study to compare trials on psychotherapy for depression with a WL control group against trials w...

Importance Suicidal ideation and suicide attempts are debilitating mental health problems that are often treated with indirect psychotherapy (ie, psychotherapy that focuses on other mental health problems, such as depression or personality disorders). The effects of direct and indirect psychotherapy on suicidal ideation have not yet been examined i...

Introduction Generalized anxiety disorder (GAD) is one of the most common mental disorders in adults. Psychotherapies are among the most recommended treatment choices for GAD, but which should be considered as first-line treatment still needs to be clarified. Objectives To examine the most effective and accepted psychotherapy for GAD both in the s...

Introduction Treating the early phase of schizophrenia is crucial for preventing further episodes and improving quality of life, functioning, and social inclusion. Pharmacotherapies are first-line treatments, but have limitations. There is consensus on the need for non-pharmacological interventions for individuals in the early phase of schizophreni...

Psychotherapies are first-line treatments for most mental disorders, but their absolute outcomes (i.e., response and remission rates) are not well studied, despite the relevance of such information for health care users, providers and policy makers. We aimed to examine absolute and relative outcomes of psychotherapies across eight mental disorders:...

Background Given the growth in research examining the effects of psychotherapy on social anxiety disorder (SAD), an up-to-date comprehensive meta-analysis in this field is needed. Methods We selected studies from a database of randomized trials (RCTs) on psychotherapies for anxiety disorders (last updated search of PubMed, PsycINFO, Embase, and Co...

Background Major depressive disorder (MDD) is highly prevalent and burdensome for individuals and society. While there are psychological interventions able to prevent and treat MDD, uptake remains low. To overcome structural and attitudinal barriers, an indirect approach of using online insomnia interventions seems promising because insomnia is les...

Psychological interventions can help reduce posttraumatic stress symptoms (PTSS) in youth, but many do not seek help. Internet- and mobile-based interventions (IMIs) show promise in expanding treatment options. However, the overall evidence on IMIs in reducing PTSS among youth remains unclear. This systematic review and meta-analysis investigated t...

Question Depression is highly prevalent and associated with numerous adverse consequences for both individuals and society. Due to low uptake of direct treatment, interventions that target related, but less stigmatising problems, such as perceived stress, have emerged as a new research paradigm.This individual participant data (IPD) meta-analysis e...

Background It is uncertain whether app-based interventions add value to existing mental health care. Objective To examine the incremental effects of app-based interventions when used as adjunct to mental health interventions. Methods We searched PubMed, PsycINFO, Scopus, Web of Science, and Cochrane Library databases on September 15th, 2023, for...

Since the 1970s, hundreds of randomized trials have examined the effects of psychotherapies for depression, and this number is increasing every year. In this study, we report outcomes from a living systematic review of these studies. We use Poisson regression analyses to examine if the proportions of studies have changed over time across the charac...

Importance Generalized anxiety disorder (GAD) is one of the most common mental disorders in adults. Psychotherapies are among the most recommended treatments for GAD, but which should be considered as first-line treatment needs to be clarified. Objective To use a network meta-analysis to examine the short- and long-term associations of different p...

Link to the online R tutorial webpage: rct-tutorial.mharrer.dev.

Background In low-resource settings, e-mental health may substantially increase access to evidence-based interventions for common mental disorders. We conducted a systematic literature search to identify randomised trials examining the effects of digital interventions with or without therapeutic guidance compared to control conditions in individual...

Background Considered one of the highest levels of evidence, results of randomized controlled trials (RCTs) remain an essential building block in mental health research. They are frequently used to confirm that an intervention “works” and to guide treatment decisions. Given their importance in the field, it is concerning that the quality of many RC...

Background It is not clear if there is an interaction between psychotherapy and pharmacotherapy. First, there may be no interaction at all, meaning that the effects of both are independent of each other. Second, antidepressants may reduce the effects of psychotherapy, and third, antidepressants may increase the effects of psychotherapy. We examined...

Initial findings indicate the effectiveness of internet-based interventions for body dysmorphic disorder (BDD). In order to substantiate these findings, a seven-module guided internet-based intervention was created and examined. We report the mixed data of participants with clinical and subclinical BDD of the treatment group ( n = 18). We investiga...

Background: It is not yet known whether psychological treatments of depression in primary care have comparable effects to treatments in specialized mental health care. We conducted a meta-analysis comparing randomized controlled trials in primary and specialized care. Methods: We selected studies from an existing database of randomized trials of...

Background: Depression is highly prevalent among individuals with chronic back pain. Internet-based interventions can be effective in treating and preventing depression in this patient group, but it is unclear who benefits most from this intervention format. Method: In an analysis of two randomized trials (N = 504), we explored ways to predict h...

Background: Over the past 16 years, we have developed a 'Meta-analytic Research Domain' (MARD) of all randomized trials of psychological treatments of depression. A MARD is a living systematic review of a research field, that cannot be otherwise covered by one (network) meta-analysis and includes multiple PICOs. In this paper we give an overview o...

Objective Behavioral activation (BA) is an extensively examined treatment for depression which is relatively simple to apply in comparison to other psychotherapies. BA aims to increase positive interactions between a person and the environment. All previous meta-analyses focused on BA in groups and guided self-help, but none focused on BA in indivi...

Genito-Pelvic Pain/Penetration-Disorder (GPPPD) is a common disorder but rarely treated in routine care. Previous research documents that GPPPD symptoms can be treated effectively using internet-based psychological interventions. However, non-response remains common for all state-of-the-art treatments and it is unclear which patient groups are expe...

Background: Excessive crying, sleeping, and feeding problems in early childhood are major stressors that can result in parents feeling socially isolated and having low self-efficacy. Affected children are a risk group for being maltreated and developing emotional and behavioral problems. Thus, the development of an innovative and interactive psych...

Cognitive behavior therapy (CBT) is by far the most examined type of psychological treatment for depression and is recommended in most treatment guide­lines. However, no recent meta‐analysis has integrated the results of randomized trials examining its effects, and its efficacy in comparison with other psychotherapies, pharmacotherapies and combine...

Most people with a mental disorder meet criteria for multiple disorders. We conducted a systematic review and meta-analysis of randomized trials comparing psychotherapies for people with depression and comorbid other mental disorders with non-active control conditions. We identified studies through an existing database of randomized trials on psych...

Background: In the past 10 years an increasing number of randomised trials have examined the effects of transdiagnostic treatments of patients with depression or anxiety. We conducted the first comprehensive meta-analysis of the outcomes of this emerging field. Methods: We used the searches in PubMed, PsychINFO, Embase and the Cochrane library o...

Introduction Digital health interventions are an effective way to treat depression, but it is still largely unclear how patients’ individual symptoms evolve dynamically during such treatments. Data-driven forecasts of depressive symptoms would allow to greatly improve the personalisation of treatments. In current forecasting approaches, models are...

BACKGROUND Excessive crying, sleeping, and feeding problems in early childhood are major stressors that can result in parents feeling socially isolated and having low self-efficacy. Affected children are a risk group for being maltreated and developing emotional and behavioral problems. Thus, the development of an innovative and interactive psychoe...

Because of the rapidly increasing number of randomised controlled trials (RCTs) and meta-analyses in many fields, there is an urgent need to step up from meta-analyses to higher levels of aggregation of outcomes of RCTs. Network meta-analyses and umbrella reviews allow higher levels of aggregation of RCT outcomes, but cannot adequately cover the ev...

Digital health applications are becoming increasingly important for assessing and monitoring the wellbeing of people suffering from mental health conditions like depression. A common target of said applications is to predict the results of self-assessed Patient-Health-Questionnaires (PHQ), indicating current symptom severity of depressive individua...

Previous studies have shown the correlation be-tween sensor data collected from mobile phones and human depression states. Compared to the traditional self-assessment questionnaires, the passive data collected from mobile phones is easier to access and less time-consuming. In particular, passive mobile phone data can be collected on a flexible time...

Previous studies have shown the correlation between sensor data collected from mobile phones and human depression states. Compared to the traditional self-assessment questionnaires, the passive data collected from mobile phones is easier to access and less time-consuming. In particular, passive mobile phone data can be collected on a flexible time...

Digital health applications are becoming increasingly important for assessing and monitoring the wellbeing of people suffering from mental health conditions like depression. A common target of said applications is to predict the results of self-assessed Patient-Health-Questionnaires (PHQ), indicating current symptom severity of depressive individua...

Zusammenfassung Zielsetzung Trotz der Effektivität verschiedener E‑Mental-Health-Interventionen wurden bislang verhältnismäßig geringe Nutzungsraten, selbst unter Digital Natives wie Studierenden, identifiziert. Ziel dieser Studie ist daher, das Verhältnis der generellen Akzeptanz, dem konkreten Interesse und der tatsächlichen Registrierung für au...

While randomized trials typically lack sufficient statistical power to identify predictors and moderators of outcome, ”individual participant data” (IPD) meta-analyses, which combine primary data of multiple randomized trials, can increase the statistical power to identify predictors and moderators of outcome. We conducted a systematic review of IP...

Objective: This experiment aims to investigate the influence of narrative information varying in the degree of perceived similarity and source credibility in supplemented testimonials on the acceptance of digital mental health services (digi-MHSs). Methods: In fall 2020, n =231 university students were randomly assigned to an active control group (...

This book serves as an accessible introduction into how meta-analyses can be conducted in R. Essential steps for meta-analysis are covered, including pooling of outcome measures, forest plots, heterogeneity diagnostics, subgroup analyses, meta-regression, methods to control for publication bias, risk of bias assessments and plotting tools. Advance...

We conducted an umbrella review of 31 meta-analyses with 608 primary studies, examining the effects of psychological interventions for prevention and treatment of mental and psychological problems in college students. The proportion of unique primary studies included in the meta-analyses ranged from 6 to 100%. For problems like depression, anxiety,...

Electronic mental health services (eMHSs) offer additional options for the dissemination of psychological interventions for university students. Still, many university students are reluctant to use eMHSs. Narrative messages may help increase the awareness and acceptance of quality-approved programs. However, little is known about the usefulness of...

Background: Many depressed patients are treated in institutional settings. The number of studies focusing on psychotherapies for depressed patients in institutional settingsis limited, and only a few up-to-date meta-analyses have integrated the results of these studies. Methods: We conducted a meta-analysis of 32 randomized trials with 37 compariso...

Depression is highly prevalent among university students. Internet-based interventions have been found to be effective in addressing depressive symptoms, but it is open if this also applies to interventions directed at academic stress. It is also largely unclear if the techniques employed in such programs provide significant additional benefits whe...

Background After remission, antidepressants are often taken long term to prevent depressive relapse or recurrence. Whether psychological interventions can be a viable alternative or addition to antidepressants remains unclear. Aims To compare the effectiveness of psychological interventions as an alternative (including delivered when tapering anti...

Introduction: Evidence on effects of Internet-based interventions to treat subthreshold depression (sD) and prevent the onset of major depression (MDD) is inconsistent. Objective: We conducted an individual participant data meta-analysis to determine differences between intervention and control groups (IG, CG) in depressive symptom severity (DSS...

Background Eating problems are highly prevalent among young adults. Universities could be an optimal setting to prevent the onset of eating disorders through psychological intervention. As part of the World Mental Health‐International College Student initiative, this systematic review and meta‐analysis synthesizes data on the efficacy of eating dis...

Mental disorders are highly prevalent and often remain untreated. Many limitations of conventional face-to-face psychological interventions could potentially be overcome through Internet-based and mobile-based interventions (IMIs). This chapter introduces core features of IMIs, describes areas of application, presents evidence on the efficacy of IM...

Internet-based and mobile interventions (IMIs) can help students to effectively cope with stress, but lacking awareness represents a barrier for adoption. While research suggests acceptance-facilitating effects of information, little is known about the additional value of testimonials in improving the uptake of IMIs for students. Objective: The aim...

Background. Eating problems are highly prevalent among young adults. Universities could be an optimal setting to prevent eating disorders through psychological intervention. As part of the World Mental Health-International College Student initiative, this systematic review and meta-analysis synthesizes data on the efficacy of eating disorder preven...

Background: Mental disorders are highly prevalent among university students. Distance-learning students are particularly burdened and have limited access to conventional university health services. Interventions for stress are sought after in distance learners and may help increase treatment coverage. Internet-based interventions have been shown to...

Stress related mental health problems are common among university students. Internet based and mobile interventions (IMIs) can help students to effectively cope with stress. However, lacking knowledge and negative attitudes may be barriers to use such interventions. While research suggests that information can be acceptance facilitating , little is...

Background: Meditation, yoga, and mindfulness are popular interventions at universities and tertiary education institutes to improve mental health. However, the effects on depression, anxiety, and stress are unclear. This study assessed the effectiveness of meditation, yoga, and mindfulness on symptoms of depression, anxiety, and stress in tertiary...