Research master thesis | Psychology (research) (MSc)
closed access
Objective: The Clinician-Administered PTSD Scale for DSM-5 (CAPS-5) is the gold standard to assess post-traumatic stress disorder (PTSD). Although the CAPS-5 was developed and validated in Western...Show moreObjective: The Clinician-Administered PTSD Scale for DSM-5 (CAPS-5) is the gold standard to assess post-traumatic stress disorder (PTSD). Although the CAPS-5 was developed and validated in Western populations, many clinicians and researchers also use it to assess PTSD in non-Western refugee populations. In this study we investigated whether PTSD as assessed with the CAPS-5 has the same structure and meaning across trauma-exposed, treatment-seeking individuals with either a Dutch (i.e. Western) background or a non-Western refugee background. Method: We evaluated commonly accepted DSM-5 PTSD factor models and tested different levels of measurement invariance (configural and scalar invariance) in a clinical sample of non-Western refugee patients (N = 710) and Dutch patients (N = 1162) suffering from prolonged complaints of psychotrauma, using confirmatory factor analyses (CFA). Results: CFAs showed that the Hybrid model of PTSD fit the data best in the Dutch and non-Western refugee subsample, as well as in the combined sample, indicating that configural invariance was met. The model representing scalar invariance showed a worse fit compared to the model representing configural invariance, indicating that factor loadings and/or symptom severity differed between the subsamples. Further investigation showed that this result could mainly be attributed to non-Western refugee patients often manifesting higher scores on the CAPS-5 items than Dutch patients. Conclusions: Non-Western refugee patients showed a similar structure of DSM-5 PTSD symptoms as Dutch patients. Furthermore, the relative contribution of the majority of symptoms to its belonging symptom cluster was similar between non-Western refugee patients and Dutch patients. This meant that both groups understood these symptoms in the same way. However, non-Western refugee patients often manifested a higher symptom severity than Dutch patients.Show less
Research master thesis | Psychology (research) (MSc)
closed access
Objective: This study aimed to clarify the relationship between the course of core depressive symptoms and the course of insomnia symptoms in older adults with a depressive disorder, and to...Show moreObjective: This study aimed to clarify the relationship between the course of core depressive symptoms and the course of insomnia symptoms in older adults with a depressive disorder, and to identify predictors of an unfavorable versus a favorable course of core depressive symptoms and insomnia symptoms. Method: We examined 329 older adults (median age 69 (IQR 65-75), 66.9% women) with a depressive disorder within the Netherlands Study of Depression in Older persons (NESDO), a naturalistic cohort study with a six-year follow-up and assessments every six months in between. Core depressive symptoms and insomnia symptoms were assessed with 14 and 3 items, respectively, from the Inventory of Depressive Symptomatology (IDS). We applied growth mixture modelling to identify classes of participants with similar trajectories of core depressive symptoms and insomnia symptoms. The association between core depressive and insomnia symptom trajectories was examined with a chi-squared test. Finally, we investigated predictors of class membership for core depressive symptoms and for insomnia symptoms using multinomial logistic regression. Results: We identified three trajectories of core depressive symptoms: high and stable (22.2% of participants were assigned to this class), moderate and declining (37.4%), and low and declining (40.4%). We identified four trajectories of insomnia symptoms: high and stable (23.1%), moderate and stable (55.6%), low and increasing (7.6%), and moderate and declining (13.7%). There was a significant association between core depressive and insomnia symptom trajectories, in particular for the most and least favorable trajectories. Number of chronic diseases, a comorbid anxiety disorder, and functional limitations predicted less favorable core depressive symptom trajectories. We found no predictors for insomnia symptom trajectories. Conclusion: Persistent insomnia symptoms are highly prevalent in older adults with depression, even in those with improving core depressive symptoms. This highlights the need for separate treatment of insomnia symptoms in addition to depression interventions.Show less
Research master thesis | Psychology (research) (MSc)
closed access
Adolescents’ future expectations (FE) regarding the attainability of desired life goals are variable, and, compared to allistic peers (i.e., non-autistics), are often more pessimistic. One reason...Show moreAdolescents’ future expectations (FE) regarding the attainability of desired life goals are variable, and, compared to allistic peers (i.e., non-autistics), are often more pessimistic. One reason may be that autistic adolescents have more difficulties on the social domain, and therefore perceive their own social competence as poorer than allistic peers. Importantly, FE may inform adolescents goal-directed actions, such that expectations for the future influence actual future outcomes. Thus, the importance of assessing which factors influence future expectations is evident. This study assessed the extent to which autistic and allistic adolescents differ on self-perceived social competence (SPSC), and FE (on the romantic and self-development domains); and the extent to which autistic adolescents’ SPSC was related to their FE compared to allistic peers, controlled for global self-esteem. Autistic adolescents’ were expected to have lower FE than allistic peers’, related to lower SPSC. Preliminarily, the uni-dimensionality and reliability of constructs was tested with factor analyses. Mediation analyses on a total of 142 adolescents, 88 allistic and 54 autistic (Mrange 12-21; Mage = 16.31, SD = 1.94), revealed that, though autism was not directly related to having less optimistic FE for either romantic or self-development goals, SPSC mediated the relationship between autism and FE for self-development (i.e., having a job/career, or continuing their education). That is, autistic adolescents’ lower SPSC was related to poorer FE for self-development compared to allistic peers, when controlled for global self-esteem. Clinical implications and future directions for research are discussed.Show less
Research master thesis | Psychology (research) (MSc)
closed access
Childhood maltreatment (CM) is a public health issue affecting mental and physical well-being of individuals across the lifespan. The literature so far suggests that CM is a risk factor for the...Show moreChildhood maltreatment (CM) is a public health issue affecting mental and physical well-being of individuals across the lifespan. The literature so far suggests that CM is a risk factor for the development and severity of EDs in adulthood. This study aims to build upon and update the findings of Molendijk et al. (2017) by integrating both pre-2016 and post-2016 literature on the relationship between all types of CM (physical, sexual, and emotional) and all types of EDs. A random-effects meta-analysis with moderator analyses was performed to assess the associations between all types of CM and all types of ED, focusing on their prevalence, severity, and related comorbid conditions. The prevalence of CM was consistently and significantly higher in ED patients (18.4- 57.7%) than in healthy controls (7.2-29.2%) and mostly higher compared to psychiatric controls (21.2 - 31.1%). The odds of developing EDs were significantly elevated in individuals exposed to CM, with ORs ranging from 2.81 to 4.60. CM exposure was associated with greater severity of EDs (r = .21, 95% CI [0.10, 0.32], p < .001) and was also associated with higher levels of depression and anxiety (r = .19, 95% CI [0.11, 0.26], p < .001). Additionally, we found that CM exposure significantly increased the likelihood of comorbid mental health disorders in patients with EDs compared to non-exposed counterparts (ORs 1.15 to 3.96), with the strongest associations observed for Axis I disorders, especially depression and anxiety. Moderator analyses revealed that recent studies reported slightly higher CM prevalence in AN samples. Sample size influenced the sexual CM-BED relationship (R2 =0.42, p =.04), and higher study quality was linked to lower prevalence rates (R2 = 0.07, p < .001), though these factors explained only a small part of the heterogeneity. Our findings highlight that all types of childhood maltreatment (physical, sexual, and emotional) are associated with a range of EDs in adulthood and influence both the severity and course of EDs.Show less
Research master thesis | Psychology (research) (MSc)
open access
Bullying victimization is a major public health concern, because victims often experience long-term negative mental health outcomes. Longitudinal brain structure research in children is needed to...Show moreBullying victimization is a major public health concern, because victims often experience long-term negative mental health outcomes. Longitudinal brain structure research in children is needed to understand the possible mechanisms underlying the relation between bullying victimization and negative mental health outcomes. Previous research has shown that the fusiform gyrus, amygdala and vmPFC are impaired in victims. Therefore, this thesis examined the relation between victimization and fusiform gyrus, amygdala and vmPFC volume over time. We hypothesized that victims of bullying, compared to children uninvolved in bullying, would have a larger fusiform gyrus volume and a steeper volume increase. Furthermore, we hypothesized that victims of bullying, compared to children uninvolved in bullying, would have a smaller amygdala and vmPFC volume and a steeper volume decrease. The sample consisted of 156 children (62% female), aged between 7 and 9 years old at baseline, from the Leiden Consortium on Individual Development. At the beginning of the study, the Revised Olweus Bully/Victim Questionnaire was administered to measure bullying victimization and high-resolution structural MRI scans were taken. This was done again two years later. Children were classified as victims if they had been bullied regularly in the past two months. We did not find an effect of victimization on fusiform gyrus, amygdala and vmPFC volume. Future research examining the influence of victimization on both structural and functional brain development is needed to provide further insights, which can help inform the design of interventions to reduce the negative consequences of bullying victimization. The current findings emphasize the importance of protective factors that make a victim’s brain development resilient against victimization. This indicates a need for interventions targeting the development of social-emotional skills or the increase of family support.Show less
Research master thesis | Psychology (research) (MSc)
closed access
Transcutaneous vagus nerve stimulation (tVNS) together with mindful acceptance hold promise for pain management, yet their combined efficacy remains largely unstudied. This study investigates...Show moreTranscutaneous vagus nerve stimulation (tVNS) together with mindful acceptance hold promise for pain management, yet their combined efficacy remains largely unstudied. This study investigates whether this combination can effectively reduce pain perception in healthy participants. We exposed 52 participants to two types of heat stimuli by using a Medoc pain device: Warm temperature of 47 °C and hot temperature of 51 °C. Subsequently, participants were divided into receiving either active tVNS (n = 26), or sham tVNS (n = 26). During the experiment, on alternating blocks, we asked participants to exercise mindful acceptance or to react naturally towards the experimentally induced heat pain. Participants rated their subjective pain by using a visual analogue slider and underwent EEG recordings to assess Contact-Heat Evoked Potentials (CHEPs). After performing several rmANOVAs, the results indicated that tVNS combined with mindful acceptance did not significantly reduce reported pain perception and neurophysiological responses, compared to the control group. However, mindful acceptance alone was associated with reduced subjective pain ratings, both for the affective (p < .001, np2 = .45) and sensory (p < .001, np2 = .39) aspects of pain, though it did not significantly reduce CHEPs (p = .82, np2 = .001). Lastly, tVNS alone did not significantly influence subjective pain ratings, both affective (p = .13, ηp² = .045) and sensory (p = .42, ηp² = .013), nor CHEPs (p = .31, np2 = .021). Overall, these findings suggest a positive effect of mindful acceptance on subjective pain perception, but future studies assessing objective measures of neurophysiological correlates during tVNS with mindful acceptance are warranted.Show less
Research master thesis | Psychology (research) (MSc)
closed access
Many situations in daily life require the simultaneous performance of motor and cognitive tasks, such as reaching for items in the supermarket while recalling a shopping list. For patients with...Show moreMany situations in daily life require the simultaneous performance of motor and cognitive tasks, such as reaching for items in the supermarket while recalling a shopping list. For patients with Parkinson’s Disease (PwPD), who already suffer from distinct motor and cognitive symptoms, these situations can be even more challenging. While deep brain stimulation (DBS) provides a promising option for symptom management in the advanced stages of the disease, its effect on everyday life situations has not been explored as much. Thus, using a dual-task paradigm, this study aimed to address this gap by investigating the effects of varying levels of cognitive load and DBS on motor and cognitive performance in PwPD. Eight PwPD with DBS were tested twice: once with DBS turned on and once off. Motor performance was assessed with a custom-designed motor task that required the patients to perform consecutive goal-directed reaching movements. These movements were recorded with a markerless hand-tracking module to capture broad motor performance measures and detailed kinematic data. Cognitive performance was assessed with a serial subtraction task, including high and low levels of cognitive load (subtracting by seven and one, respectively). Finally, linear mixed-effect models were used to statistically compare the effects of DBS, high, and low cognitive load on overall motor and cognitive performance and relevant kinematic features. The results show that high cognitive load negatively affected overall motor and cognitive performance, while low cognitive load only affected cognitive performance. On the other hand, DBS improved overall motor performance while not affecting cognitive performance. Furthermore, high cognitive load and DBS had a significant, yet opposite, effect on the same kinematic features: deceleration time, movement time, reaction time, peak velocity, and coefficient of variation of trajectory error. In conclusion, this study highlights the feasibility of administering more naturalistic experimental designs with a dual-task paradigm and detailed kinematic analyses in PwPD. We show that the dual-task effect is dependent on the amount of cognitive load and that Deep Brain Stimulation can significantly improve motor performance in dual-tasking scenarios. Finally, our detailed kinematic analyses reveal specific components of a reaching movement responsible for changes in motor performance, providing valuable insights for future research and clinical practice.Show less
Research master thesis | Psychology (research) (MSc)
under embargo until 2025-07-31
2025-07-31T00:00:00Z
We tested the effects of audit probability (high, low, ambiguous) and audit probability change (increase, decrease) on compliance in a simplified tax return task. Participants were asked to report...Show moreWe tested the effects of audit probability (high, low, ambiguous) and audit probability change (increase, decrease) on compliance in a simplified tax return task. Participants were asked to report correct returns, faced with either a high (40%), low (10%) or ambiguous (10-40%) audit probability. In addition, audit probabilities of each participant were either increased or decreased by five percentage points after half of all trials were completed. Results showed that, in line with our predictions, high audit probability yielded significantly higher compliance than low audit probability and that high and ambiguous audit probability yielded similar compliance. Contrary to our expectations, audit probability change in the form of increases or decreases did not yield significant effects on compliance. The present study indicates that an ambiguous audit probability can yield increased compliance akin to a high audit probability. Our findings provide a starting point for further investigation into the effects of information about audit probability on tax compliance. Suggestions for replication studies and further research are provided.Show less
Research master thesis | Psychology (research) (MSc)
closed access
Adolescence is characterized by the onset of puberty. Puberty, in turn is shown to be a driver of brain development and has been related to the onset and increase of internalizing symptoms. However...Show moreAdolescence is characterized by the onset of puberty. Puberty, in turn is shown to be a driver of brain development and has been related to the onset and increase of internalizing symptoms. However, the relationship between puberty, brain development, and internalizing symptoms has not been studied using multiple pubertal measures in both sexes. Here we examine the mediating role of brain development on the relationship between puberty and internalizing symptoms. Pubertal status, timing, age at menarche, and internalizing symptoms were assessed based on self-reports in 160 adolescents between 10 and 25 using a three-wave accelerated longitudinal design. Structural MRI scans were only obtained in the first wave. Subsequently, the relations between the pubertal measures (status, timing, age at menarche) and internalizing symptoms were tested as well as their relations with grey matter thickness and volume in frontal, cingulate, and subcortical areas. Only age at menarche as a timing variable had a significant effect on internalizing symptoms at T1 in girls (ß = -.36, p = .002, 95% CI [-.68, -.17]). Mediation models revealed no significant mediation of grey matter thickness and volume in our ROIs. Other effects did not reach significance or became non-significant after Bonferroni corrections. These findings indicate that menstruating before one’s peers is a risk factor for developing internalizing symptoms. This highlights the importance of supporting early menstruating girls to possibly prevent them from developing internalizing symptoms. Replication studies are needed to assess the accuracy of our results.Show less
Research master thesis | Psychology (research) (MSc)
closed access
Building on evidence that minority representation increases minorities’ political participation, in my preregistered study, I investigated whether increased racial representation within the climate...Show moreBuilding on evidence that minority representation increases minorities’ political participation, in my preregistered study, I investigated whether increased racial representation within the climate movement causes Americans of color (N = 226) to evaluate the climate movement more positively and to encourage them to partake in climate activism. I tested this by using a 2 x 2 between-subjects design in which representation was manipulated both descriptively (i.e., the presence of people of color) and substantively (i.e., a focus on issues specifically affecting people of color) in a short video about climate activism. The results showed that descriptive representation had a positive, significant effect on evaluation of the movement, but no effects were found for substantive representation nor on climate action behavior. These findings enrich the scientific literature and provide insights on how social movements can become more inclusive, potentially increasing their effectiveness.Show less
Research master thesis | Psychology (research) (MSc)
under embargo until 2026-03-29
2026-03-29T00:00:00Z
Relevance: Efficacy of doctor empathy and nocebo education on treatment outcomes of people with cancer has been established across experimental and randomised-controlled trials (RCT). Objective: i)...Show moreRelevance: Efficacy of doctor empathy and nocebo education on treatment outcomes of people with cancer has been established across experimental and randomised-controlled trials (RCT). Objective: i) to test whether distinct effects of clinician empathy and nocebo information can also improve psychological and side effect outcomes of clinical advanced breast cancer patients undergoing chemotherapy and ii) to explore whether potential positive effects are persistent over treatment time. Methods: In this 2x2 proof-of-principle study, before treatment start, a total of 23 Dutch, chemonaïve, female breast cancer patients undergoing chemotherapy were randomised (1:1:1:1) to short information videos on chemotherapy side effects. The four videos varied on levels of empathy (+ / -) and nocebo information (+ / -). During treatment, participants’ psychological (primary outcomes: anxiety, distress) and side effect outcomes were assessed by self-report questionnaires at 7-days, 21-days, and 52-days after treatment start. Results: Repeated linear mixed model analyses indicated that empathy generally did not affect the level of anxiety (p = .440) or distress (p = .056). Empathy increased overall intensity (β = 0.76, 95% CI [.07; 1.44], p = .032) and number of side effects (β = 0.78, 95% CI [.11; 1.45], p = .025). Nocebo information did not seem to influence intensity (p = .269) or number of side effects (p = .975). Only anxiety levels were indicated to increase over time (p = .008), both at 21-days (β = 0.86, 95% CI [.25; 1.47]) and 52-days (β = 1.18, 95% CI [.38; 1.98]) post-treatment start. Conclusions: In clinical settings, advanced breast cancer patients may not profit from empathy or nocebo information. Repeating the study with a larger sample is recommended to gain clarity on communication effects. The information videos may benefit training of clinical staff and treatment consultations.Show less
Research master thesis | Psychology (research) (MSc)
closed access
Cooperation and competition are important aspects of group behavior that have been well-researched in social psychology, but the relation between these elements has not been investigated to a...Show moreCooperation and competition are important aspects of group behavior that have been well-researched in social psychology, but the relation between these elements has not been investigated to a comparable degree. While competition between groups is known to increase cooperation within groups, the precise magnitude of its influence is not clear. Theoretically-relevant moderators that could influence this relationship have been left largely unexplored, and influential methods of studying cooperation and competition have not been assessed. Therefore, in this pre-registered meta-analysis, we investigated the impact of between-group interactions, including outright between-group competition and situations where groups compare their performance to other groups, on within-group cooperation. We conducted a systematic review of the literature involving economic games that compare cooperation in the presence of an intergroup interaction to cooperation within single groups. We compiled 17 relevant studies which yielded 47 effect sizes. Our multilevel random effects model revealed a small-to-medium, positive effect of intergroup interaction on within-group cooperation (g = 0.505, N = 4187). Confirmatory moderator analyses indicated that males, compared to females, invested more in within-group cooperation during intergroup interactions than in single, isolated groups. Additionally, effects involving intergroup comparison were weaker than effects featuring intergroup competition. Exploratory moderator analyses revealed that several variations in the methods of study impact the effect on within-group cooperation (e.g. deception, decision type, and participant matching). Our findings present compelling meta-analytic evidence that intergroup competition has a reliable impact on cooperation, and raises several opportunities for future research.Show less
Research master thesis | Psychology (research) (MSc)
closed access
Avoidance is a hallmark symptom of Post-Traumatic Stress Disorder (PTSD), yet the link between avoidance learning and PTSD severity and treatment outcome has not yet been explored. For this purpose...Show moreAvoidance is a hallmark symptom of Post-Traumatic Stress Disorder (PTSD), yet the link between avoidance learning and PTSD severity and treatment outcome has not yet been explored. For this purpose, we administered a computer-based avoidance learning task to 144 treatment-seeking PTSD patients during the baseline assessment of a randomized clinical trial. The task consisted of a photo of blue or red colored lamps (conditional stimuli, CS+) followed by aversive photos (unconditional stimulus, US), while a photo of a yellow-colored lamp was followed by a black screen (safety stimulus, CS-). The US could be avoided by pressing a button during one CS+ (CS+ avoidable) but not the other (CS+ unavoidable). Participants were asked to fill in a threat expectancy rating after the CSs, and to report their relief after omission of the US. Participants were then given exposure therapy, and their PTSD symptoms were measured throughout 52 weeks. We predicted that higher rates of unnecessary or ineffective avoidance, higher expectancy ratings after omission of the US, and higher relief scores would relate to higher PTSD severity, and lower treatment gains. Results did not confirm any hypothesis; however, elevated threat expectancies (regardless of CStype) were related to PTSD symptom severity at baseline, and expectancies following CS- were related to PTSD severity across time points. Findings suggest general impairment in action-safety learning; however, it might be more relevant in light of PTSD severity to further explore the role of general threat expectancy. Furthermore, future studies should consider utilizing physiological measures, and adapting the task to include avoidance costs.Show less
Research master thesis | Psychology (research) (MSc)
closed access
In this study we investigated the relationship between stress, prosociality, and academic achievement. With a sample of UK-based college students, we aimed to investigate whether prosociality may...Show moreIn this study we investigated the relationship between stress, prosociality, and academic achievement. With a sample of UK-based college students, we aimed to investigate whether prosociality may serve as a buffer for the assumed negative relationship between stress and academic achievement. Our findings revealed that there was a negative relationship between academic stress and academic achievement. Furthermore, people tended to be more prosocial when they were stressed. However, this increased prosociality was not related to academic achievement and did not buffer people’s academic achievement from the negative effects of stress. The findings highlight the complex dynamic between stress, prosociality, and academic achievement. Understanding the interplay between these three variables has significant value for the innovation of interventions and preventive measures to enhance the overall well-being in students.Show less
Research master thesis | Psychology (research) (MSc)
under embargo until 2026-02-27
2026-02-27T00:00:00Z
Food waste is a big problem in the Netherlands. In an effort to find a solution to this problem, the present study examines the influence of expiration date labels on people’s intention to waste...Show moreFood waste is a big problem in the Netherlands. In an effort to find a solution to this problem, the present study examines the influence of expiration date labels on people’s intention to waste food. The current phrase “ten minste houdbaar tot” [“at least preservable until”] can be seen as definitive and thought to refer to food safety whereas it refers to food quality, thus this study proposes an alternative phrase “beste kwaliteit voor, vaak goed na” [“best quality before, often good after”]. The aim of this alternative phrase was to make clear that the expiration date refers to food quality and that the food could still be safe to consume after this date had passed. Participants were presented with dairy and pantry products that had an expiration date that had passed by five days. This expiration date was shown with the current phrasing or the alternative phrasing. Results showed that the alternative phrase led to a lower intention to waste dairy compared to the current phrase. Whereas for pantry products, there was no difference in intention to waste food between the two phrases. Moreover, results showed that the intention to waste dairy was mediated by perceived risk. Meaning that dairy products that were presented with the alternative phrase were perceived as less risky to consume, which in turn was associated with a lower intention to let the product go to waste when the expiration had passed. Thus, changing the phrasing of the expiration date label could help in reducing food waste in the Netherlands.Show less
