Autism spectrum conditions (ASC) encompass a range of sensory, motor, and social-communicative differences, reflecting the considerable heterogeneity within the autism spectrum. This diversity underscores the limitations of categorical diagnostic approaches, which often fail to capture the individualized manifestations of autism. Advances in genetics and neuroscience have driven a shift towards dimensional frameworks that emphasize the spectrum nature of autism and the broad autism phenotype (BAP). BAP encapsulates subclinical traits that mirror those of autism in the general population, challenging the conventional boundaries between clinical and non-clinical populations. Furthermore, sensorimotor differences, which are particularly prevalent in individuals with ASC, follow a spectrum-like pattern similar to the BAP and are predictive of developmental outcomes related to social participation, communication, and overall quality of life in people with and without ASC. However, specific descriptions of these relationships are lacking.

This dissertation investigated the complex relationships between sensorimotor differences and autistic traits (ATs). Through a series of five interconnected studies, we examined broad sensory processing patterns and specific sensory modalities, namely auditory processing and motor/proprioception, to explore their roles in autistic phenotypes.

Study 1 of the dissertation validated a Swedish translation of the Broad Autism Phenotype Questionnaire (BAPQ). By examining parents' BAP traits, the study highlighted significant associations between higher ATs and having a child with ASC. Furthermore, it confirmed the presence of all three AT domains—social interaction (AT_SOC), communication (AT_COM), and cognitive rigidity (AT_RIG), reinforcing the genetic and phenotypic continuity between clinical and subclinical ATs.

Study 2 and Study 3 served as broader investigations into all seven sensory modalities and their associations with ATs. Study 2 explored these modality-specific associations, using Bayesian stochastic search variable selection (SSVS) and dominance analysis. This study highlighted auditory processing difficulties as the most consistent predictor of all three AT domains. Additionally, proprioceptive and tactile processing difficulties were specifically associated with AT_COM and AT_SOC, respectively.

Study 3 extended this analysis to a developing population, focusing on the relationship between sensorimotor processing, ATs, and anxiety in children aged 6-11 years. Identical to Study 2, we found tactile symptoms as a predictor of AT_SOC, proprioceptive symptoms for AT_COM, and auditory symptoms for AT_RIG. In addition, olfactory symptoms were selected as a predictor of AT_COM, and motor coordination was a consistent predictor of all AT domains. Using SSVS, this study also identified that auditory and olfactory processing difficulties were strong predictors of anxiety symptoms.

Building on the previous studies, Study 4 narrowed the focus to auditory processing differences, investigating specific auditory problems and their associations with the AT domains. All AT domains significantly predicted affective reactions to sounds, while difficulties with speech perception, spatial perception, and auditory stream segregation were most strongly predicted by AT_COM.

Study 5 focused on the previously found links between motor coordination and proprioceptive processing and AT_COM. Using causal mediation analysis within a counterfactual framework, this study found that cerebellar error correction deficits, measured through a finger tapping task, significantly impacted AT_COM through motor skills in childhood.

Together, this dissertation provides a comprehensive overview of the sensory processing dimensions related to the core AT domains. Specifically, the studies underscored the clinical significance of monitoring auditory and olfactory complaints in children, as these were predictive of anxiety, and emphasized that early motor deficits impact social communication development. The findings advocate for the inclusion of detailed sensory and motor assessments in neurodevelopmental evaluations to identify children at risk for poor mental health outcomes. Future research should continue to explore the mechanisms underlying sensory processing differences. Particular focus should be placed on auditory and motor/proprioceptive functions and their contributions to ATs and clinical outcomes, such as anxiety. Emphasis should also be given to longitudinal studies that track these relationships over time.

Background. Decreased sound intolerance (DST) is a disabling transdiagnostic phenomenon with high clinical relevance in autism. Neurodevelopmental DST is often studied as part of a general multisensory construct that includes both hyper- and hyposensitivity. Therefore, knowledge about the potential relevance of individual differences in the auditory modality is lacking. The purpose of the study was to begin to differentiate between commonly pooled auditory functions, by incorporating psychometric tools from the field of audiology. 

Methods. In a pilot sample (N = 520 adults, 23% autistic), we used Bayesian correlations to quantify the contribution of individual auditory items from the Glasgow Sensory Questionnaire to the degree of social, communicative and rigid autistic traits measured with the Broad Autism Phenotype Questionnaire (BAPQ) subscales. Then, we recruited an independent sample (N = 175 adults, 18% autistic) to measure, more specifically, 1) emotional reactions to sounds (affective DST), 2) speech understanding difficulties, and 3) non-social auditory processing (spatial perception and stream segregation), using self-report questionnaires. We used multiple regressions to test for associations with the autistic trait domains. 

Results. We found that all autistic traits measured by the BAPQ (social, communicative and rigid) linearly predicted affective DST, and these associations remained when autistic participants were excluded. Difficulties with speech perception, as well as spatial perception and auditory stream segregation, were most strongly predicted by communication differences. 

Conclusion. The robust relationship between autistic traits and emotional sound reactivity suggest that affective DST falls on a spectrum just like autism. This argues against strict dichotomization and encourages the use of continuous measures. The results support a dominant role for emotional and stress systems in autism-related DST, and may suggest that detailed audiological tests are clinically useful, in particular in the context of pragmatic language difficulties. 

Sensory processing differences measured by self- or parent-report co-segregate with quantitative autistic traits and have potential endophenotypic properties. It is not known to what extent this reflects generalized sensory dysfunction versus more specific associations involving individual senses or autistic trait domains. We combined Bayesian variable selection with dominance analysis to obtain a more nuanced understanding of modality-specific associations. We recruited two independent samples of adults to complete the Broad Autism Phenotype Questionnaire and the Glasgow Sensory Questionnaire. For each domain of autistic traits (social interaction, communication, cognitive rigidity), we performed stochastic search variable selection using Glasgow Sensory Questionnaire modality subscales as predictors while controlling for uncertainty in other variables. Dominance analysis was applied to the reduced models to evaluate the relative importance of predictors. Only auditory scores reliably predicted all three autistic traits when other modalities were accounted for. The proprioceptive scale, which included motor and interoceptive deficits, predicted communicative autistic traits more than other trait domains. The tactile scale appeared most specific for social autistic traits. Although the findings must be interpreted in light of the limitations of the questionnaires, the study suggests that auditory differences may be more likely than differences in other senses to be a robust sensory endophenotype relevant to autism. Lay abstract Sensory symptoms are a major source of distress for many autistic people, causing anxiety, stress, and avoidance. Sensory problems are thought to be passed on genetically together with other autistic characteristics, such as social preferences. This means that people who report cognitive rigidity and autistic-like social function are more likely to suffer from sensory issues. We do not know what role the individual senses, such as vision, hearing, smell, or touch, play in this relationship, because sensory processing is generally measured with questionnaires that target general, multisensory issues. This study aimed to investigate the individual importance of the different senses (vision, hearing, touch, smell, taste, balance, and proprioception) in the correlation with autistic traits. To ensure the results were replicable, we repeated the experiment in two large groups of adults. The first group contained 40% autistic participants, whereas the second group resembled the general population. We found that problems with auditory processing were more strongly predictive of general autistic characteristics than were problems with the other senses. Problems with touch were specifically related to differences in social interaction, such as avoiding social settings. We also found a specific relationship between proprioceptive differences and autistic-like communication preferences. The sensory questionnaire had limited reliability, so our results may underestimate the contribution of some senses. With that reservation in mind, we conclude that auditory differences are dominant over other modalities in predicting genetically based autistic traits and may therefore be of special interest for further genetic and neurobiological studies.

The broad autism phenotype (BAP) is a set of characteristics often observed in typically developing people with a genetic load for autism, such as parents of autistic children. The Broad Autism Phenotypic Questionnaire (BAPQ) is a 36-item questionnaire developed to identify the BAP in first-degree relatives of autistic people. We translated the BAPQ into Swedish and examined its psychometric properties in a Swedish sample consisting of 45 parents of children with ASC and 74 parents of non-autistic children. We found support for the original 3-factor structure (aloof, pragmatic language and rigid), good internal consistency and convergent validity with the Autism Quotient. Thus, the Swedish BAPQ exhibits acceptable psychometric properties and may be useful for assessing the BAP in non-clinical populations.

Background: Autistic adults have an elevated risk of many health problems compared with the general population, making health care access extra critical. Unfortunately, autistic people often find health care settings quite aversive, and many medical providers report feeling unsure about how to interact with autistic patients. We aimed at characterizing specific challenges regarding sensory experiences and communicative barriers in health care settings.

Methods: We recruited adults to complete an anonymous online questionnaire on the topic of improving healthcare experiences for everyone. The questions covered demographics, sensory experiences in medical settings, and communication with health care providers. We quantified the associations between autism diagnosis and experiences of sensory discomfort and communication barriers in health care settings. We also did a qualitative analysis of text responses to questions on how to improve sensory environments and communication with providers.

Results: Swedish adults (62 autistic and 36 nonautistic) participated in the study. The cohort was well educated, and autistic participants received their autism diagnosis late in life (median age 36 years, range 13–57). Compared with nonautistic participants, autistic participants reported greater discomfort with background sound levels in health care settings and felt more misunderstood by health care providers. Thematic analyses showed that auditory stimuli and proximity to other people were particularly bothersome for autistic participants, causing stress or avoidance and affecting the ability to interact with providers. Providers contributed to communication barriers by failing to recognize the need for individualized information, especially when respondents’ difficulties were not visible or taken seriously. Participants requested greater clarity and supplementary written information. Providers also misunderstood autistic adults’ body language or eye contact patterns, as they interpreted their clients through the lens of neurotypical expectations.

Conclusions: Our results extend previous research by emphasizing sensory aspects of health care settings and suggesting specific and reasonable adaptations. The results also highlight how the provider’s implicit expectations of nonverbal communication caused misinterpretations of autistic people who were socially skilled but did not use typical body language. Based on the data, we suggest specific adaptations, many of which may also benefit nonautistic people.

Social anxiety disorder (SAD) is a highly prevalent and impairing disorder. Current bestpractice is cognitive behavioral therapy (CBT), but there are several challenges associatedwith performing exposure therapy. Virtual reality exposure (VRE) may improvetreatment efficacy of SAD in a group therapy context, because it allows for greatercontrol, flexibility, and individualization of the exposure stimuli. However, to date nostudy has investigated the use of VRE for SAD in a group context. In the present study,nine patients who had undergone group CBT with VRE for SAD and three therapistsresponsible for the treatment were interviewed about their experiences. The objective ofthe study was to investigate the practical and therapeutic challenges of using VRE in agroup therapy context. Thematic analysis was used to analyze the data. The resultsshowed that it was difficult for the patients to engage with the VRE in a group therapycontext and that there were several practical challenges. However, all participants foundthe VRE exercises to be meaningful, because it gave them a medium to practice andunderstand typically avoided social situations. The latter has not previously beendescribed as a treatment mechanism for anxiety through virtual reality. However, theappropriateness of VRE in group therapy remains unclear. Implications are discussed.

Multisensory temporal integration could be compromised in both autism spectrum disorders (ASD) and schizophrenia spectrum disorders (SSD) and may play an important role in perceptual and cognitive impairment in these two disorders. This review aimed to quantitatively compare the sensory temporal acuity between healthy controls and the two clinical groups (ASD and SSD). Impairment of sensory temporal integration was robust and comparable in both patients with SSD (Hedges’ g = 0.91, 95%CI[0.62–1.19]; Z = 6.21, p < .001) and ASD (Hedges’ g = 0.85, (95%CI[0.54–1.15]; Z = 5.39, p < .001). By further separating studies into unisensory and multisensory (bimodal: audiovisual) ones, subgroup analysis indicated heterogeneous and unstable effects for unisensory temporal binding in the ASD group, but a more consistent and severe impairment in multisensory temporal integration represented by an enlarged temporal binding window in both clinical groups. Such multisensory dysfunction is associated with symptoms like hallucinations and impaired social communications. Future studies focusing on improving multisensory temporal functions may have important implications for the amelioration of schizophrenia and autistic symptoms.

Autism spectrum conditions (ASC) and quantitative autistic traits (QATs) are associated with sensory symptoms, which may contribute to anxiety and adversely affect social and cognitive development. Although sensory symptoms can occur across all senses, the relative roles of specific sensory modalities as contributors to the autistic phenotype and to anxiety are not well understood. The objective of this study was to examine which sensory symptoms were most predictive of high anxiety. We recruited 257 female primary caregivers of children aged 6 to 11 years (49 % girls) to a questionnaire study comprising parent-report measures for classical QATs (social, communicative, and rigid), autism-related sensorimotor symptoms (visual, auditory, tactile, olfactory, gustatory, vestibular, proprioceptive, and motor), and anxiety symptoms. First, Bayesian stochastic search variable selection (SSVS) was used to identify the most probable sensorimotor predictors of specific QATs as well as diagnosed ASC. Then, the selected predictors were used in another SSVS, using anxiety symptoms as a dependent variable, to identify which of the autism-relevant sensorimotor symptoms were most robustly predictive of anxiety. Finally, the effect sizes of anxiety-related sensory symptoms were estimated with linear regressions. We found that auditory symptoms and motor difficulties were most predictive of ASC diagnosis. Developmental motor difficulties were also strongly related to all individual QATs, whereas auditory symptoms were more selectively predictive of rigid traits. Tactile symptoms robustly predicted social interaction QATs, and proprioceptive symptoms predicted communicative QATs. Anxiety outcomes were most predicted by difficulties with auditory and olfactory processing. The results support the clinical importance of being alert to complaints about sounds and hearing in neurodevelopmental populations, and that auditory processing difficulties may be evaluated as an early marker of poor mental health in children with and without diagnosed autism. Olfactory processing differences appeared to be an anxiety marker less strongly associated with ASC or QATs, while motor difficulties were highly autism-relevant but not equally strongly associated with anxiety outcomes. We suggest that future studies may focus on the mechanisms and consequences of neurodevelopmental central auditory processing dysfunction and its potential relationship to anxiety disorders.

Early motor function is important for emerging social pragmatic communication (SPC) skills in both typical and atypical development. However, the nature of motor impairments relevant for higher-level communication is not well understood. Inefficient cerebellar error correction might directly cause both developmental coordination disorder (DCD) symptoms and SPC difficulties, through the extensive communication between cerebellar zones and brain-wide sensorimotor and higher-order networks. DCD symptoms related to cerebellar deficits could also impact SPC through affecting the developmental trajectory of social development, which requires motor skills. This study aimed to test the hypothesis that error correction deficits affect SPC outcomes through childhood DCD symptoms, by using contemporary causal inference methodology. We used a finger tapping task and computational modeling to measure cerebellar error correction in adult participants (n = 138), and quantified childhood DCD symptoms and SPC skills using psychometric measures. The results confirmed that error correction ability likely affects SPC skills, and indicated that childhood motor skills significantly mediated this. These results argue against a direct effect of domain-general error correction deficits on SPC, and instead suggest that cerebellum-related DCD symptoms affect sociocommunicative development more directly through motor deficits during development. Further research is required to test whether cerebellar error correction could be used as an early marker to identify children in need for early SPC interventions.