Mark van der Gaag

Vrije Universiteit Amsterdam | VU · Department of Clinical Psychology

Background Recent stressful life events (SLE) are a risk factor for psychosis, but limited research has explored how SLEs affect individuals at clinical high risk (CHR) for psychosis. The current study investigated the longitudinal effects of SLEs on functioning and symptom severity in CHR individuals, where we hypothesized CHR would report more SL...

ACT in Daily Life (ACT-DL) is a blended-care Ecological Momentary Intervention that extends ACT into the daily life of individuals, improving psychotic distress, negative symptoms, and global functioning. However, it remains unclear whether ACT-DL works equally for everyone. We investigated whether moderators (i.e., sociodemographic information, pe...

The effect of psychological treatment on social functioning, quality of life and autism traits in autistic people with suicidal behaviour remains largely unknown. At six Dutch mental health centres, 123 adult outpatients with Diagnostic and Statistical Manual of Mental Disorders (5th edition) diagnosed autism spectrum condition and suicidal behavio...

Trauma and post‐traumatic stress are involved in the aetiology and maintenance of voice‐hearing. It has been proposed that trauma‐focused therapy (TFT) might affect voice‐hearing, but previous studies are limited and remain undecided. Objectives We aimed to investigate the effect of TFT on voice‐hearing in people with PTSD and psychosis using expe...

Background: Safety behaviors, both positive (maladaptive coping behavior) and negative (avoidance behavior), are used by people with paranoid delusions to avoid perceived threats. Safety behaviors contribute to the persistence of paranoid delusions by preventing disconfirmation of threat beliefs and may influence other psychiatric symptoms. This st...

Aim To compare psychotic‐like experiences (PLEs) in adolescents and young adults referred to the Mental Health Services (MHSs). Methods Participants scored the 16‐item Prodromal Questionnaire (PQ‐16) as part of the intake procedure. Data on the Diagnostic and Statistical Manual of Mental Disorders (DSM) classification and demographic data were col...

Purpose For many individuals with a psychotic disorder societal recovery is not accomplished. Research on societal recovery trajectories is mostly focussed on patients with a first episode psychosis. The present study aims to identify distinct societal trajectories in those with long duration of illness, through the identification of patient subgro...

Background and Hypothesis Cognition has been associated with socio-occupational functioning in individuals at Clinical High Risk for Psychosis (CHR-P). The present study hypothesized that clustering CHR-P participants based on cognitive data could reveal clinically meaningful subtypes. Study Design A cohort of 291 CHR-P subjects was recruited thro...

Background Technology improves accessibility of psychological interventions for youth. An ecological momentary intervention (EMI) is a digital intervention geared toward intervening in daily life to enhance the generalizability and ecological validity, and to be able to intervene in moments most needed. Identifying working mechanisms of the use of...

Background Virtual Reality cognitive behavioral therapy (VR‐CBT) has proven to be an effective treatment method for paranoia and anxiety in psychosis. However, it is unknown, which individuals benefit most from VR‐CBT. Previous studies examined factors affecting the treatment effect of regular CBTp, including illness duration, paranoia, depression,...

Introduction Studies have consistently demonstrated increased stress sensitivity in individuals with psychosis. Since stress sensitivity may play a role in the onset and maintenance of psychosis, this could potentially be a promising target for treatment. The current study was the first to investigate whether reactivity to and recovery from daily-l...

Backgrounds Many autistic people in mental health are suicidal. This study evaluated the effectiveness of dialectical behavior therapy (DBT) v. treatment as usual (TAU) in reducing suicidal ideation and suicide attempts. Methods At six Dutch mental health centers, 123 outpatients (18–65 years) with DSM-5 diagnosed autism spectrum disorder (ASD) an...

Background Pre-diagnostic stages of psychotic illnesses, including ‘clinical high risk’ (CHR), are marked by sleep disturbances. These sleep disturbances appear to represent a key aspect in the etiology and maintenance of psychotic disorders. We aimed to examine the relationship between self-reported sleep dysfunction and attenuated psychotic sympt...

Background Temstem is a smartphone app developed with and for clinical voice hearing individuals with the aim to reduce their voice hearing distress and improve social functioning. Methods A randomized controlled trial with adult outpatients suffering from distressing and frequent auditory verbal hallucinations (AVH) was conducted. Participants we...

BACKGROUND Acceptance and Commitment Therapy (ACT) is promising in the treatment of early psychosis. Augmenting face-to-face ACT with a mobile health (mHealth) ecological momentary intervention (EMI) may increase its treatment effects and empower clients to take treatment into their own hands. OBJECTIVE This study aimed to investigate treatment en...

Background Acceptance and commitment therapy (ACT) is promising in the treatment of early psychosis. Augmenting face-to-face ACT with mobile health ecological momentary interventions may increase its treatment effects and empower clients to take treatment into their own hands. Objective This study aimed to investigate and predict treatment engagem...

Background Psychotic experiences (PEs) and social isolation (SI) seem related during early stages of psychosis, but the temporal dynamics between the two are not clear. Literature so far suggests a self-perpetuating cycle wherein momentary increases in PEs lead to social withdrawal, which, subsequently, triggers PEs at a next point in time, especia...

Importance Targeting low self-esteem in youth exposed to childhood adversity is a promising strategy for preventing adult mental disorders. Ecological momentary interventions (EMIs) allow for the delivery of youth-friendly, adaptive interventions for improving self-esteem, but robust trial-based evidence is pending. Objective To examine the effica...

ACT in Daily Life (ACT-DL) is a blended-care Ecological Momentary Intervention that extends ACT into the daily life of individuals, improving psychotic distress, negative symptoms, and global functioning. However, it remains unclear whether ACT-DL works equally for everyone. We investigated whether moderators (i.e., sociodemographic information, pe...

Background Persecutory delusions are strong threat beliefs about others’ negative intentions. They can have a major impact on patients’ day-to-day life. The Feeling Safe Programme is a new translational cognitive-behaviour therapy that helps patients modify threat beliefs and relearn safety by targeting key psychological causal factors. A different...

Background: Suicidal ideation (SI) and suicide attempts (SA) are common in autistic individuals, but prevalence rates have not yet been estimated with meta-analysis. Aims: This meta-analysis aims to estimate SI and SA prevalence rates in autistic individuals and identify subgroup differences based on sample characteristics and study quality. Method...

Aim: Identifying multimorbid psychopathology is necessary to offer more adequate treatment and ultimately reduce the prevalence of persistent mental illnesses. Psychotic symptoms are increasingly seen as a transdiagnostic indicator of multimorbidity, severity and complexity of non-psychotic psychopathology. This study aims to investigate whether p...

Background: Persecutory delusions are strong threat beliefs about others’ negative intentions. They can have a major impact on patients’ day-to-day life. The Feeling Safe Programme is a new translational cognitive-behavior therapy that helps patients modify threat beliefs and relearn safety by targeting key psychological causal factors. A different...

Background and objectives: Many people with a psychotic disorder are coping with severe psychosocial limitations related to their illness. The current randomized controlled trial (RCT) investigates the effects of an eating club intervention (HospitalitY (HY)) aimed to improve personal and societal recovery. Methods: In 15 biweekly sessions parti...

Aims: Evidence for case-control studies suggests that cannabis use is a risk factor for the development of psychosis. However, there have been limited prospective studies and the direction of this association remains controversial. The primary aim of the present study was to examine the association between cannabis use and the incidence of psychot...

Individuals at clinical high risk (CHR) for psychosis have been found to have altered cytokine levels, but whether these changes are related to clinical outcomes remains unclear. We addressed this issue by measuring serum levels of 20 immune markers in 325 participants (n=269 CHR, n=56 healthy controls) using multiplex immunoassays, and then follow...

We aimed to examine determinants of criminal victimization (i.e. both personal and property crime victimization) in outpatients with severe mental illness.Data was collected using a multisite epidemiological survey including a random sample of 956 adult outpatients with SMI. Data on 12-month victimization prevalence and frequency were obtained usin...

Concern for symptom exacerbation and treatment drop-out is an important barrier to the implementation of trauma-focused therapy (TFT), especially in people with a psychotic disorder. This study, which was part of a multicenter randomized controlled trial, investigated posttraumatic stress disorder (PTSD) symptom exacerbation during eye movement des...

Background Adverse childhood experiences (ACE) can affect educational attainments, but little is known about their impact on educational achievements in people at clinical high risk of psychosis (CHR). Methods In total, 344 CHR individuals and 67 healthy controls (HC) were recruited as part of the European Community’s Seventh Framework Programme-f...

Background and hypothesis Around 20% of people at clinical high risk (CHR) for psychosis later develop a psychotic disorder, but it is difficult to predict who this will be. We assessed the incidence of hearing speech (termed speech illusions [SIs]) in noise in CHR participants and examined whether this was associated with adverse clinical outcomes...

BACKGROUND AND HYPOTHESIS: Around 20% of people at clinical high risk (CHR) for psychosis later develop a psychotic disorder, but it is difficult to predict who this will be. We assessed the incidence of hearing speech (termed speech illusions [SIs]) in noise in CHR participants and examined whether this was associated with adverse clinical outcome...

Introduction Many people with psychotic disorders experience symptoms of post-traumatic stress disorder (PTSD). In recent years, several trauma-focused therapies (TFTs), including cognitive restructuring (CR), prolonged exposure (PE), and eye movement desensitization and reprocessing (EMDR) have been studied and found to be safe and effective in re...

Background: Temstem is a mobile application developed in cooperation with voice-hearing persons to help them cope with distressing voices. After psychoeducation about voice hearing, Temstem offers two functions: Silencing is a mode designed to inhibit voice activity through the processing of incompatible language; the Challenging mode introduces du...

The Positive Memory Training (PoMeT) trial demonstrated reduced depression symptoms at 3 months for schizophrenia, but its longer-term outcome and cost impacts remain unknown. This study is a within-trial cost-utility analysis with quality-adjusted life years (QALYs) as outcome based on health-related quality of life (HRQoL) measurement and seconda...

Background and hypothesis: Around 20% of people at clinical high-risk (CHR) for psychosis later develop a psychotic disorder, but it is difficult to predict who this will be. We assessed the incidence of hearing speech (termed speech illusions) in noise in CHR participants and examined whether this was associated with adverse clinical outcomes. Stu...

Introduction Social connectedness might positively influence the course of clinical symptoms in people with psychotic disorders. Objectives This study examines satisfaction with social connectedness (SSC) as predictor of positive and negative symptoms in people with a psychotic disorder. Methods Data from the Pharmacotherapy Monitoring and Outcom...

Introduction: Many people with psychotic disorders experience symptoms of post-traumatic stress disorder (PTSD). In recent years, several trauma-focused therapies (TFTs), including cognitive restructuring (CR), prolonged exposure (PE), and eye movement desensitization and reprocessing (EMDR) have been studied and found to be safe and effective in r...

Objective People at ultra-high risk (UHR) for psychosis have a high prevalence of tobacco smoking, and rates are even higher among the subgroup that later develop a psychotic disorder. However, the longitudinal relationship between the course of tobacco smoking and clinical outcomes in UHR subjects is unknown. Methods We investigated associations...

Objective To examine the association between baseline alterations in grey matter volume (GMV) and clinical and functional outcomes in people at clinical high risk (CHR) for psychosis. Methods 265 CHR individuals and 92 healthy controls were recruited as part of a prospective multi-centre study. After a baseline assessment using magnetic resonance...

Background Low self-esteem is a relevant transdiagnostic condition in the etiology, manifestation, and aggravation of different types of psychopathology. While low self-esteem is expected to ameliorate automatically after successful treatment of the principal emotional disorder the patient is suffering from, this does not always happen. Therefore,...

Background Screening methods for detecting Ultra High Risk status (UHR) or psychosis should be improved, especially in adolescent samples. We therefore tested whether the Child Behavior Checklist (CBCL) and the Youth Self Report (YSR) add value to the Prodromal Questionnaire-16 items version (PQ-16) for detecting UHR status or psychosis. Methods W...

Introduction/objective: This study aimed to investigate efficacy of Acceptance and Commitment Therapy in Daily Life (ACT-DL), combining face-to-face therapy with an Ecological Momentary Intervention (EMI), in addition to treatment as usual (TAU) for psychotic distress, in comparison to TAU. Methods: Individuals aged 15-65 years with clinically e...

Background We investigated treatment effects of Acceptance and Commitment Therapy in Daily Life (ACT-DL) on psychological flexibility (PF) and the moderating role of the therapeutic working alliance on these effects in patients with early psychosis. Methods ACT-DL is an ecological momentary intervention (EMI) combining face-to-face ACT with a smar...

Background Post-traumatic mechanisms are theorised to contribute to voice-hearing in people with psychosis and a history of trauma. Phenomenological links between trauma and voices support this hypothesis, as they suggest post-traumatic processes contribute to the content of, and relationships with, voices. However, research has included small samp...

Background Psychotic features have been part of the description of the borderline personality disorder (BPD) ever since the concept “borderline” was introduced. However, there is still much to learn about the presence and characteristics of delusions and about the stability of both hallucinations and delusions in patients with BPD. Methods A follo...

Background Negative symptoms occur in individuals at ultrahigh risk (UHR) for psychosis. Although there is evidence that observer ratings of negative symptoms are associated with level of functioning, the predictive value of subjective experience in daily life for individuals at UHR has not been studied yet. Objective This study therefore aims to...

Purpose Migrant and ethnic minority populations exhibit a higher incidence of psychotic disorders. The Ultra-High Risk for psychosis (UHR) paradigm provides an opportunity to explore the stage at which such factors influence the development of psychosis. In this systematic review, we collate and appraise the literature on the association between et...

[This corrects the article DOI: 10.3389/fpsyt.2020.609530.].

Purpose: This study examines satisfaction with social connectedness (SSC) as predictor of positive and negative symptoms in people with a psychotic disorder. Methods: Data from the Pharmacotherapy Monitoring and Outcome Survey (PHAMOUS) was used from patients assessed between 2014 and 2019, diagnosed with a psychotic disorder (N = 2109). Items a...

Background The high prevalence rates and impact of tobacco smoking in individuals with a psychotic disorder have become an increasing interest. Little is known about tobacco smoking in individuals at ultra-high risk of psychosis (UHR). Methods We studied 345 UHR individuals of the high-risk study of the European network of national schizophrenia n...

Robust deficits in cognitive functioning are present in people with psychosis and are evident in the early stages of the disorder. Impairments in verbal memory and verbal fluency are reliably seen in individuals at clinical high-risk for psychosis (CHR) compared to healthy populations. As previous studies have shown a relationship between cognition...

Background: The high prevalence of smoking in individuals who are at ultra-high risk (UHR) for psychosis is well known and moderate cognitive deficits have also been found in UHR. However, the association between smoking and cognition in UHR is unknown and longitudinal studies are lacking. Method: A cohort study with 330 UHR individuals and 66 c...

Background Targeting low self-esteem in youth exposed to childhood adversity is a promising strategy for preventing adult mental disorder, but psychological help remains difficult to access and accept for youth, calling for novel, youth-friendly approaches. Mobile Health (mHealth) and, most prominently, ecological momentary interventions (EMIs) pro...

[This corrects the article DOI: 10.1093/schizbullopen/sgaa033.].

Introduction Diagnoses of anxiety and/or depression are common in subjects at Ultra-High Risk for Psychosis (UHR) and associated with extensive functional impairment. Less is known about the impact of affective comorbidities on the prospective course of attenuated psychotic symptoms (APS). Method Latent class mixed modelling identified APS traject...

Important questions remain about the profile of cognitive impairment in psychotic disorders across adulthood and illness stages. The age-associated profile of familial impairments also remains unclear, as well as the effect of factors, such as symptoms, functioning, and medication. Using cross-sectional data from the EU-GEI and GROUP studies, compr...

Serum neuronal autoantibodies, such as those to the NMDA receptor (NMDAR), are detectable in a subgroup of patients with psychotic disorders. It is not known if they are present before the onset of psychosis or whether they are associated with particular clinical features or outcomes. In a case-control study, sera from 254 subjects at clinical high...

PurposeMigrant status is one of the most replicated and robust risk factors for developing a psychotic disorder. This study aimed to determine whether migrant status in people identified as Ultra-High Risk for Psychosis (UHR) was associated with risk of transitioning to a full-threshold psychotic disorder.Methods Hazard ratios for the risk of trans...

BACKGROUND Acceptance and Commitment Therapy (ACT) is promising in the treatment of early psychosis. Augmenting face-to-face ACT with a mobile health (mHealth) ecological momentary intervention (EMI) may increase its treatment effects and empower clients to take treatment into their own hands. OBJECTIVE This study aimed to investigate treatment ad...

Importance Treatment in the early stages of psychosis is crucial to prevent poor clinical and social outcomes. Currently, no preventive interventions are available that reduce psychotic distress, or affective and negative symptoms as well as functioning, calling for more and dedicated treatments for these. Objective To investigate the efficacy of A...

Aims Childhood trauma is associated with an elevated risk for psychosis, but the psychological mechanisms involved remain largely unclear. This study aimed to investigate emotional and psychotic stress reactivity in daily life as a putative mechanism linking childhood trauma and clinical outcomes in individuals at ultra-high-risk (UHR) for psychosi...

BACKGROUND Negative symptoms occur in individuals at ultrahigh risk (UHR) for psychosis. Although there is evidence that observer ratings of negative symptoms are associated with level of functioning, the predictive value of subjective experience in daily life for individuals at UHR has not been studied yet. OBJECTIVE This study therefore aims to...

Background Recovery in schizophrenia is a complex process, involving clinical, societal and personal recovery. Until now, studies analysed these domains separately, without examining their mutual relations and changes over time. Aims This study aimed to examine different states of recovery and transition rates between states. Method The Pharmacot...

Abstact Despite empirical evidence for multifactorial causes of voice-hearing, people's own beliefs about what caused their voices are understudied. People with distressing voices (n=125) completed measures of trauma, post-traumatic stress disorder (PTSD) symptoms, and beliefs about causality. Most participants reported trauma in the past (97%) and...

Despite increased prevalence of domestic violence and abuse (DVA), victimization through DVA often remains undetected in mental health care. To estimate the effectiveness of a system provider level training intervention by comparing the detection and referral rates of DVA of intervention community mental health (CMH) teams with rates in control CMH...

Patients with a psychotic disorder have certain symptoms, movement disorders resulting from the pharmacological effects of medication. Knowing about this is important to the patients' dental treatment. A very small group will present with delusions about teeth or the benevolent or malevolent intentions of the dentist. Negative symptoms are an impor...