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

  • 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


    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


    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


    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


    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


    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


    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


    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