Bio


I am an early career researcher with a PhD from the University of Melbourne, Australia. I am currently working in a postdoctoral position at Stanford, where I am involved in several research projects focusing on measurement development, phenotypic characterisation, and advancing insights into the heterogeneity of autism. My primary research interest is to better understand heterogeneity in autism presentation as a stepping stone towards developing more individualised assessment and support.

Stanford Advisors


All Publications


  • The Utility of the Five Factor Model of Personality as an Organizing Framework for Autism-Related Traits. Assessment Widjaja, E. S., Spackman, E. K., Bainbridge, T. F., Ludeke, S. G., Uljarevic, M., Hudry, K., Smillie, L. D. 2025: 10731911251326395

    Abstract

    Growing research suggests that clinical psychological traits are contiguous with normal personality and can be located within the same psychometric frameworks. In this article, we examined whether autism-related traits (ARTs) can plausibly be located within the Five Factor Model (FFM) of personality. Across two studies (Ns = 408 and 423), participants completed measures of ARTs, broad FFM domains, and narrower FFM facets. We used empirically derived criteria to evaluate whether ARTs overlapped (i.e., shared variance) with the FFM domains to a degree that was comparable to FFM facets. Results suggested that most socially oriented ARTs could be represented as facets of the extraversion domain, whereas behaviorally oriented ARTs were more peripheral to the FFM. Cognitively oriented ARTs were less consistently linked with the FFM. These findings highlight the value of the FFM as an organizing framework for ARTs, marking an important step toward synthesis across the personality and autism literatures.

    View details for DOI 10.1177/10731911251326395

    View details for PubMedID 40163595

  • The autism phenotype and transdiagnostic dimensional frameworks. Developmental medicine and child neurology Chetcuti, L. C., Spackman, E. K., Frazier, T. W., Whitehouse, A. J., Uljarević, M. 2025

    Abstract

    A reliable and valid diagnostic classification system is pivotal for guiding clinical decision-making, facilitating rigorous and reproducible research findings, informing population-level health planning and resource allocation, and promoting well-being. However, the current categorical approaches, while foundational, have inherent limitations, including symptom overlap between diagnostic categories, heterogeneity, instability, unreliability, and a limited capacity to quantify individual variations. We outline several challenges regarding the diagnostic conceptualization of autism and propose how transdiagnostic dimensional alternatives might facilitate a more comprehensive understanding, assessment, and clinical care for this complex clinical condition. Research Domain Criteria and Hierarchical Taxonomy of Psychopathology are two distinct yet complementary dimensional approaches that have garnered the most empirical attention. In this review, we outline the central tenets of each approach in turn and explore their potential applications in enhancing understanding and addressing challenges associated with autism in both research and clinical practice.

    View details for DOI 10.1111/dmcn.16303

    View details for PubMedID 40126448

  • Parsing the heterogeneity of social motivation in autism. Journal of child psychology and psychiatry, and allied disciplines Chetcuti, L., Hardan, A. Y., Spackman, E., Loth, E., McPartland, J. C., Frazier, T. W., Youngstrom, E. A., Uljarevic, M. 2025

    Abstract

    Social motivation is posited as a key factor in the expression of the autism phenotype. However, lack of precision in both conceptualization and measurement has impeded a thorough understanding of its diverse presentation and associated outcomes. This study addresses this gap by identifying subgroups of autism characterized by deficits in distinct facets of social motivation, relative to normative benchmarks.Data were from 509 participants with autism, aged 5-to-21 years (M = 10.43, SD = 3.67; 81% male), enrolled in the Healthy Brain Network. Latent profile analysis was employed to identify subgroups characterized by unique configurations of reticence, seeking, and maintaining facets of social motivation, derived from a comprehensive multi-instrument factor analysis of symptom and screening measures. Pearson's chi-square tests and one-way analysis of variance were performed to explore subgroup differences in demographic characteristics, cognitive abilities, co-occurring psychopathologies, and other aspects of social functioning.Four distinct subgroups were identified: Engaged (n = 247), exhibiting the fewest challenges across each area; Inhibited (n = 143), characterized by high reticence, mild challenges in seeking, and few challenges in maintaining; Aloof (n = 68), characterized by challenges with seeking and maintaining but relatively low reticence; and Avoidant (n = 52), characterized by the highest challenges across all areas. Subgroups did not differ in terms of chronological age or sex. The Engaged subgroup exhibited the fewest challenges in other aspects of social functioning and co-occurring psychopathologies, while the Avoidant subgroup exhibited the greatest challenges, and with the Inhibited and Aloof profiles falling in between.This study highlights the heterogeneous nature of deficits in social motivation in autism relative to normative benchmarks, suggesting potential avenues for tailored interventions aimed at addressing the specific challenges experienced by individuals within each subgroup. Nevertheless, there remains a need to develop more refined measurement tools capable of capturing even finer-grained aspects and diverse expressions of social motivation, facilitating further characterization of individual differences across diagnostic boundaries.

    View details for DOI 10.1111/jcpp.14147

    View details for PubMedID 40091308

  • Exploring the Heterogeneity of Self-Injurious Behaviors in Autistic Youth: Patterns, Predictors, and Implications for Intervention. Autism research : official journal of the International Society for Autism Research Ferguson, E. F., Spackman, E., Cai, R. Y., Hardan, A. Y., Uljarević, M. 2024

    Abstract

    Self-injurious behaviors (SIB) encompass a heterogeneous set of self-inflicted aggressive behaviors that are highly prevalent in autistic youth. Existing research on SIB in autism spectrum disorder (ASD) has been limited by significant methodological and conceptual inconsistencies. Thus, the current study leveraged item-level data capturing the severity of unique SIB topographies to further understanding of factors associated with distinct SIB in a sample of 582 autistic youth (Mage = 12.12, SDage = 3.68; range: 3-19 years; 13% females). Results suggest variation in severity endorsements for specific SIB topographies amongst autistic youth, such that 30%-50% of caregivers endorsed slight to very serious concern regarding the SIB topographies of bites nails/skin/fingers, scratches self, hits head/face/neck, bangs head against things, and picks skin. Generalized additive models demonstrated distinct patterns of associations between each SIB topography and dysregulation, sensory hypersensitivity, age, sex, IQ, and language level. Findings underscore the importance of exploring SIB as a multifaceted construct to capture unique correlates of distinct SIB that vary in severity and functional impact, which is critical for the development of effective interventions. This study represents an important step towards more individualized characterization of SIB and support for diverse presentations of these behaviors in autistic youth.

    View details for DOI 10.1002/aur.3269

    View details for PubMedID 39578711

  • RESTRICTED AND REPETITIVE BEHAVIORS IN YOUTH WITH ASD: A QUALITATIVE CHARACTERIZATION Spackman, E., Geng, A., Uljarevic, M. ELSEVIER SCIENCE INC. 2024: S279
  • CHARACTERIZING ASSOCIATIONS BETWEEN CLINICAL FEATURES AND DIVERSE TOPOGRAPHIES OF SELF-INJURIOUS BEHAVIORS IN AUTISTIC YOUTH Ferguson, E. F., Spackman, E., Hardan, A., Uljarevic, M. ELSEVIER SCIENCE INC. 2024: S328
  • COMBINING META-ANALYTIC AND BIG DATA APPROACHES TO DEVELOP AND VALIDATE A NEW QUANTITATIVE MEASURE AND INCREASE UNDERSTANDING OF RESTRICTED AND REPETITIVE BEHAVIORS Uljarevic, M., Spackman, E., Hardan, A. ELSEVIER SCIENCE INC. 2024: S312
  • CAPITALIZING ON EXISTING MULTI-METHOD ASD REPOSITORIES: FROM NOSOLOGY TO GENETICS IN THE CONTEXT OF RESTRICTED AND REPETITIVE BEHAVIORS Uljarevic, M., Wang, Y., Spackman, E., Hardan, A., Gratten, J. ELSEVIER SCIENCE INC. 2024: S352-S353
  • Characterizing associations between emotion dysregulation, anxiety, and repetitive behaviors in autistic youth with intellectual disability. Autism research : official journal of the International Society for Autism Research Ferguson, E. F., Spackman, E., Cai, R. Y., Hardan, A. Y., Uljarević, M. 2024

    Abstract

    There is a paucity of research that explores associations between emotion dysregulation and the expression and severity of core and co-occurring characteristics of autism spectrum disorder (ASD), especially in autistic youth with co-occurring intellectual disability (ID). This study explored the interplay between developmental characteristics and emotion dysregulation, anxiety, and specific subtypes of RRBs that are elevated in autistic youth with co-occurring ID. Generalized additive models demonstrated that age, sex, language level, dysregulation, and anxiety showed unique patterns of association with subtypes of RRBs in a sample of 150 autistic youth with co-occurring ID who are non-speaking or minimally verbal. More specifically, higher anxiety levels were significantly associated with elevations in repetitive sensory motor behaviors (RSMB), self-injurious behaviors (SIB), insistence on sameness (IS), and unusual interests (UI). While emotion dysregulation was a significant predictor of UI, it demonstrated positive, albeit not significant, associations with the intensity of SIB and RSMB. Language level was a significant predictor of RSMB, such that the intensity of RSMB was higher for individuals who were non-speaking relative to those who spoke in single words. These findings provide preliminary insights into patterns of associations between emotion dysregulation, anxiety, and specific subdomains of RRBs in autistic youth with ID.

    View details for DOI 10.1002/aur.3207

    View details for PubMedID 39166396

  • Characterising Insistence on Sameness and Circumscribed Interests: A Qualitative Study of Parent Perspectives. Journal of autism and developmental disorders Spackman, E., Geng, A., Smillie, L. D., Frazier, T. W., Hardan, A. Y., Alvarez, G. A., Whitehouse, A., Schuck, R. K., Leekam, S. R., Uljarević, M. 2024

    Abstract

    Manifestations of insistence on sameness (IS) and circumscribed interests (CI) are complex, with individuals varying considerably, not only in the types of behaviours they express, but also in terms of a behaviour's frequency, intensity, trajectory, adaptive benefits, and impacts. However, current quantitative RRB instruments capture only certain aspects of these behaviours (e.g., mostly frequency or general "severity"). Thus, the current study utilised a semi-structured caregiver interview to provide an in-depth, qualitative characterization of different aspects of IS and CI presentation. Caregivers of 27 autistic children and adolescents displaying IS and/or CI behaviours (3-16 years; 18 males; 9 females) participated in a semi-structured interview. Responses were analysed using thematic framework analysis. Framework analysis identified nine different aspects of IS and CI presentation: (1) intensity, (2) frequency, (3) emergence of behaviour, (4) changes over time, (5) day-to-day fluctuations, (6) purpose/adaptive benefit, (7) experiences of distress, (8) challenges for the individual, their family, and their socialisation, and (9) management strategies and their effectiveness. Autistic children and adolescents were reported to vary greatly on each of these dimensions. Findings demonstrate the complexity of IS and CI presentations and highlight the need for more comprehensive quantitative assessments that independently assess the frequency, intensity, and impact of behaviours. Further, findings reported here emphasize the need for ecologically valid measures that assess the contexts in which these behaviours occur and how their presentations can change within and across days.

    View details for DOI 10.1007/s10803-024-06404-4

    View details for PubMedID 38809473

    View details for PubMedCentralID 4543385

  • CHARACTERIZING MECHANISMS UNDERPINNING INSISTENCE ON SAMENESS IN CHILDREN AND ADOLESCENTS WITH ASD Pascale, I., Spackman, E., Hardan, A., Uljarevic, M. ELSEVIER SCIENCE INC. 2023: S294-S295
  • Characterizing subdomains of insistence on sameness in autistic youth. Autism research : official journal of the International Society for Autism Research Spackman, E., Smillie, L. D., Frazier, T. W., Hardan, A. Y., Uljarevic, M. 2023

    Abstract

    Insistence on sameness (IS) encompasses a range of behavioral patterns, including resistance to change, routines, and ritualized behaviors, that can be present across social and non-social contexts. Given the breadth of behaviors encompassed by IS, it is important to determine whether this domain is best conceptualized and measured as uni- or a multi-dimensional construct. Therefore, the current study aimed to characterize the structure of IS and explore potentially distinct of patterns of associations between identified IS factors and relevant correlates, including age, sex, IQ, anxiety, social abilities, emotional and behavioral dysregulation, and sensory hypersensitivity. Exploratory graph analysis was conducted using the dimensional assessment of restricted and repetitive behaviors to examine the structure of IS in a sample 1892 autistic youth (Mage =10.82, SDage =4.14; range: 3-18years; 420 females) recruited from the Simons Foundation Powering Autism Research for Knowledge cohort. Three distinct IS subdomains labeled as IS-Ritualistic/sameness, IS-Routines, and IS-Others (referring to IS behaviors during interactions with others)were identified. Generalized additive models demonstrated that each of the IS subdomains showed a unique pattern of association with key variables. More specifically, while sensory hypersensitivity was significantly associated with IS-Ritualistic/sameness and IS-Routines, it was not associated with IS-Others. Further, while emotional dysregulation was a unique predictor of IS-Ritualistic/sameness (but not IS-Routines or IS-Others), social interaction abilities were a unique predictor of IS-Routines (but not IS-Ritualistic/sameness or IS-Others). Current findings provide preliminary evidence that the IS may encompass several distinct subdomains.

    View details for DOI 10.1002/aur.3033

    View details for PubMedID 37735979

  • Arriving at the empirically based conceptualization of restricted and repetitive behaviors: A systematic review and meta-analytic examination of factor analyses. Clinical psychology review Uljarevic, M., Spackman, E. K., Whitehouse, A. J., Frazier, T. W., Billingham, W., Condron, P., Hardan, A., Leekam, S. R. 2023; 103: 102286

    Abstract

    An empirically based understanding of the factor structure of the restricted and repetitive behaviors (RRB) domain is a prerequisite for interpreting studies attempting to understand the correlates and mechanisms underpinning RRB and for measurement development. Therefore, this study aimed to conduct a systematic review and meta-analysis of RRB factor analytic studies. Sets of meta-analyses were performed to examine (a) the factor structure of individual RRB instruments, (b) associations between RRB subdomains across instruments, and (c) the association between RRB factors and other variables. Searches for peer-reviewed articles evaluating the factor structure of the RRB domain were performed in PsycINFO (Ovid), Medline (Ovid), and Embase (Ovid). No age, measurement, or informant-type limits were imposed. Quality and risk of bias for individual studies were assessed using relevant COSMIN sections. Among the 53 studies retained for review, 41 examined RRB factor structures among individuals with autism spectrum disorder (ASD) and 12 among non-ASD samples. Meta-analysis of factor correlations provided evidence that the RRB domain encompasses the following eight specific factors: repetitive motor behaviors, insistence on sameness, restricted interests, unusual interests, sensory sensitivity, and repetitive, stereotyped language. Although interrelated, RRB factors were distinct, showing a unique pattern of associations with demographic, cognitive, and clinical correlates. Meta-analyses of the associations between RRB factors and specific correlates, specifically adaptive functioning and communication impairments, should be considered preliminary due to the limited number of studies. Despite limitations, this review provides important insights into the factor structure of the RRB domain and highlights critical conceptual, measurement, and methodological limitations of the current research that will need to be addressed in order to improve our understanding of RRB.

    View details for DOI 10.1016/j.cpr.2023.102286

    View details for PubMedID 37269778

  • Profiles of circumscribed interests in autistic youth. Frontiers in behavioral neuroscience Spackman, E., Smillie, L. D., Frazier, T. W., Hardan, A. Y., Alvares, G. A., Whitehouse, A., Uljarevic, M. 2023; 17: 1037967

    Abstract

    Circumscribed interests (CI) encompass a range of different interests and related behaviors that can be characterized by either a high intensity but otherwise usual topic [referred to as restricted interests (RI)] or by a focus on topics that are not salient outside of autism [referred to as unusual interests (UI)]. Previous research has suggested that there is pronounced variability across individuals in terms of the endorsement of different interests, however, this variability has not been quantified using formal subtyping approaches. Therefore, using Latent Profile Analysis in a sample of 1,892 autistic youth (Mage = 10.82, SDage = 4.14; 420 females), this study aimed to identify subgroups based on the RU and UI profiles. Three profiles of autistic individuals were identified. They were characterized as Low CI, Predominantly RI, and Predominantly UI. Importantly, profiles differed on several key demographic and clinical variables, including age, sex composition, IQ, language level, social and communication abilities, anxiety, and obsessive-compulsive behaviors. Although replication across other samples is needed, the profiles identified in this study are potentially promising for future research given their distinct profiles of RI and UI and unique patterns of associations with key cognitive and clinical variables. Therefore, this study represents an important initial step towards more individualized assessment and support for diverse presentations of CI in autistic youth.

    View details for DOI 10.3389/fnbeh.2023.1037967

    View details for PubMedID 36844650

  • Dimensional Assessment of Restricted and Repetitive Behaviors: Development and Preliminary Validation of a New Measure. Journal of the American Academy of Child and Adolescent Psychiatry Uljarević, M., Frazier, T. W., Jo, B., Scahill, L., Youngstrom, E. A., Spackman, E., Phillips, J. M., Billingham, W., Hardan, A. 2022

    Abstract

    This paper provides initial validation of the Dimensional Assessment of Restricted and Repetitive Behaviors (DARB)-a new parent-report measure designed to capture the full range of key of restricted and repetitive behaviors (RRB) subdomains.Parents of 1892 children and adolescents with autism spectrum disorder (ASD) (M= 10.81 years; SD= 4.14) recruited from the Simons Foundation Powering Autism Research for Knowledge (SPARK) research match completed the DARB, several existing RRB instruments, and measures of social and communication impairments and anxiety. A subsample of 450 parents completed the DARB after two weeks to evaluate test-retest stability.Exploratory graph analysis (EGA) conducted in the exploratory subsample identified eight dimensions that were aligned with our hypothesized RRB subdomains: repetitive sensory motor behaviors (RSMB), insistence on sameness (IS), restricted interests (RI), unusual interests (UI), sensory sensitivity (SS), self-injurious behaviors (SIB), obsessions and compulsive behaviors (OCB) and repetitive language (RL). The confirmatory application of the exploratory structural equation modeling conducted in the confirmatory subsample showed that the derived factor structure had a good fit to the data. Derived factors had excellent reliability, convergent and divergent validity, very strong test-retest stability, and showed a distinct pattern of associations with key demographic cognitive and clinical correlates.DARB will be useful in a variety of research and clinical contexts considering the prominence and clinical impact of RRB in ASD. The strong preliminary evidence indicates that the new scale is comprehensive and captures a wide range of distinct RRB subdomains not simultaneously captured by any of the existing instruments.

    View details for DOI 10.1016/j.jaac.2022.07.863

    View details for PubMedID 36526162

  • Characterizing restricted and unusual interests in autistic youth. Autism research : official journal of the International Society for Autism Research Spackman, E., Smillie, L., Frazier, T. W., Hardan, A. Y., Alvares, G. A., Whitehouse, A., Uljarević, M. 2022

    Abstract

    A broad range of interests characterized by unusual content and/or intensity, labeled as circumscribed interests (CI), are a core diagnostic feature of autism. Recent evidence suggests that a distinction can be drawn between interests that, although characterized by unusually high intensity and/or inflexibility, are otherwise common in terms of their content (e.g., an interest in movies or animals), labeled as restricted interests (RI), and interests that are generally not salient outside of autism (e.g., an interest in traffic lights or categorization), labeled as unusual interests (UI). The current study aimed to further characterize RI and UI by exploring their association with age, sex, IQ, and social motivation, as well as to examine differences in the adaptive benefits and negative impacts of these two subdomains. Parents of 1892 autistic children and adolescents (Mage  = 10.82, SDage  = 4.14; 420 females) completed an online survey including the Dimensional Assessment of Restricted and Repetitive Behaviors and the Social Communication Questionnaire. Both RI and UI were found to be highly frequent. Sex-based differences were observed in the content, but not intensity, of CI such that females were more likely to show interests with a social component. Finally, RI and UI showed distinct patterns of association with age, sex, IQ, and social motivation, as well as metrics of adaptive benefits and negative impacts. Findings afford a more nuanced understanding of sex-based differences in CI and, crucially, provide preliminary evidence that RI and UI represent distinct constructs that should be studied independently in future research.

    View details for DOI 10.1002/aur.2863

    View details for PubMedID 36453155

  • Understanding the heterogeneity of anxiety in autistic youth: A person-centered approach. Autism research : official journal of the International Society for Autism Research Spackman, E., Lerh, J. W., Rodgers, J., Hollocks, M. J., South, M., McConachie, H., Ozsivadjian, A., Vaughan Van Hecke, A., Libove, R., Hardan, A. Y., Leekam, S. R., Simonoff, E., Frazier, T. W., Alvares, G. A., Schwartzman, J. M., Magiati, I., Uljarevic, M. 2022

    Abstract

    The present study aimed to examine anxiety profiles among children and adolescents on the autism spectrum. It further aimed to characterize the association between the identified anxiety profiles and key clinical and developmental variables. The Spence Children's Anxiety Scale-Parent Version (SCAS-P) data from a large international pooled sample of 870 caregivers of autistic children and adolescents (Mage =11.6years, SDage =2.77; 107 females) was used. Latent profile analysis identified a three-anxiety profile solution exhibiting high entropy (0.80) and high latent profile probabilities, with good classification accuracy. Identified profiles fell along the severity spectrum and were named as the mild (n=498), moderate (n=272) and severe (n=100) anxiety profiles. There were no statistically significant differences between the three anxiety profiles in terms of sex distribution. Participants in the mild profile were significantly younger than those in the severe profile, had significantly fewer social communication difficulties than youth in the moderate anxiety profile group and had significantly fewer restricted and repetitive behaviors and lower cognitive functioning scores compared to participants in moderate and severe anxiety profiles. This is the first study to move beyond identifying associations and group-level differences to exploring and identifying characteristics of anxiety-based subgroups at an individual level that differ on key clinical and developmental variables. The subgroups identified in this study are a preliminary, yet important, first step towards informing future assessment and individualized interventions aiming to support young people on the autism spectrum to reduce and manage anxiety. LAY SUMMARY: This study tried to understand if there are subgroups of autistic young people who may have similar anxiety profiles. We found that we could meaningfully group young people into three groups based on how severe the anxiety symptoms their caregivers reported were: a group with low levels of anxiety, those with moderate anxiety, and those with more severe anxiety. We also found that the young people in the mild group were younger, had fewer autism traits and lower levels of intellectual functioning than young people in the other two groups.

    View details for DOI 10.1002/aur.2744

    View details for PubMedID 35642170

  • Daily living skills scale: Development and preliminary validation of a new, open-source assessment of daily living skills. Frontiers in psychiatry Uljarević, M., Spackman, E. K., Cai, R. Y., Paszek, K. J., Hardan, A. Y., Frazier, T. W. 2022; 13: 1108471

    Abstract

    Autistic individuals and individuals with a range of other neurodevelopmental conditions (NDD) often present with lower levels of daily living skills (DLS) when compared to their neurotypical peers. Importantly, lower levels of DLS have been linked to a range of negative outcomes, including lower rates of post-secondary education, lower employment rates, and higher daily support needs across autism and NDD. However, there are currently no open-source informant-reported instruments for capturing key aspects of DLS. This study describes the development, refinement, and initial psychometric evaluation of a new, relatively brief (53-item). Daily Living Skills Scale (DLSS) in a sample of 1,361 children aged 2-17 years, Confirmatory Factor Analysis demonstrated an excellent fit of unidimensional model to the data (CFI = 0.953, TLI = 0.951, RMSEA = 0.073 [95% CI: 0.071-0.074]). The single-factor CFA model showed evidence of measurement invariance of factor loadings, thresholds, and residual variance (strict invariance) across sex, age, race, and ethnicity. Model reliability and internal consistency were excellent (ω = 0.98; α = 0.97). Conditional reliability estimates indicated very good reliability (= 0.80) for the total DLS scale from very low (θ = -4.2) to high (θ = +2.4) scores. Conceptually derived self-care, homecare, and community participation subscales also showed strong reliability and internal consistency. With further replication, the EFS has excellent potential for wide adoption across research and clinical contexts.

    View details for DOI 10.3389/fpsyt.2022.1108471

    View details for PubMedID 36756637

    View details for PubMedCentralID PMC9900738