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Many autistic children experience changes in core symptom severity across middle childhood, when co-occurring mental health conditions emerge. We evaluated this relationship in 75 autistic children from 6 to 11 years old. Autism symptom severity change was evaluated for total autism symptoms using the autism diagnostic observation schedule calibrated severity score, as well as social-communication symptoms calibrated severity score, and restricted/repetitive behaviors calibrated severity score. Children were grouped based on their symptom severity change patterns. Mental health symptoms (attention-deficit hyperactivity disorder, anxiety, disruptive behavior problems) were assessed via parental interview and questionnaire and compared across the groups. Co-occurring mental health symptoms were more strongly associated with change in social-communication symptom or restricted/repetitive behavior severity than with total autism symptom severity. Two relevant groups were identified. The social-communication symptom-increasing-severity-group (21.3%) had elevated and increasing levels of anxiety, attention-deficit hyperactivity disorder, and disruptive behavior problems compared with children with stable social-communication symptom severity. The restricted/repetitive behavior-decreasing-severity-group (22.7%) had elevated and increasing levels of anxiety; 94% of these children met criteria for an anxiety disorder. Autism symptom severity change during middle childhood is associated with co-occurring mental health symptoms. Children that increase in social-communication symptom severity are also likely to demonstrate greater psychopathology, while decreases in restricted/repetitive behavior severity are associated with higher levels of anxiety. For many autistic children, the severity of their autism symptoms changes during middle childhood. We studied whether these changes are associated with the emergence of other mental health challenges such as anxiety and attention-deficit hyperactivity disorder. Children who had increased social-communication challenges had more anxiety and attention-deficit hyperactivity disorder symptoms and disruptive behavior problems than other children. Children who decreased their restricted and repetitive behaviors, on the contrary, had more anxiety. We discuss why these changes in autism symptoms may lead to increases in other mental health concerns. [ABSTRACT FROM AUTHOR]

One of the most universally accepted facts about autism is that it is heterogenous. Individuals diagnosed with autism spectrum disorder have a wide range of behavioral presentations and a variety of co-occurring medical and mental health conditions. The identification of more homogenous subgroups is likely to lead to a better understanding of etiologies as well as more targeted interventions and treatments. In 2006, we initiated the UC Davis MIND Institute Autism Phenome Project (APP) with the overarching goal of identifying clinically meaningful subtypes of autism. This ongoing longitudinal multidisciplinary study now includes over 400 children and involves comprehensive medical, behavioral, and neuroimaging assessments from early childhood through adolescence (2–19 years of age). We have employed several strategies to identify sub-populations within autistic individuals: subgrouping by neural, biological, behavioral or clinical characteristics as well as by developmental trajectories. In this Mini Review, we summarize findings to date from the APP cohort and describe progress made toward identifying meaningful subgroups of autism. [ABSTRACT FROM AUTHOR]

Studies evaluating change in autism symptom severity across the lifespan have yielded inconsistent results, making it difficult to assess the prevalence of meaningful change in autism symptom severity, and what characterizes it. Better understanding the ways in which autism symptoms change over time is crucial, with important implications for intervention. Synthesizing information across past studies, autism symptom severity change (especially decreases) appears common, though stability of symptoms is also frequent. Symptom severity change is characterized by variability in patterns of change between different individuals (between-person), variability in change within a person's trajectory across time (within-person), and variability in change patterns across symptom domains (i.e., social-communication, restricted/repetitive behaviors). Variability in severity change is likely impacted by differences in person-level characteristics (e.g., sex, IQ, sociodemographic factors) as well as developmental processes across time. Numerous methodological issues may impact our ability to understand how common change in symptom severity is, including varying measurement tools, analytic approaches, and change patterns between symptom domains across time. Potential implications of better understanding and characterizing symptom severity change include incorporation of severity change patterns and predictors of change into research on biomarkers, and consideration of such predictors as moderators or mediators of change in clinical practice. • Change in autism symptom severity over time, especially decreases, is common. • Symptom severity change is variable between and within individuals and subdomains. • Variability is impacted by individual characteristics and developmental processes. • Methodological issues impact conclusions that can be drawn about severity change. • Understanding symptom change is relevant for biomarker research and clinical use. [ABSTRACT FROM AUTHOR]

The amygdala is widely implicated in both anxiety and autism spectrum disorder. However, no studies have investigated the relationship between co-occurring anxiety and longitudinal amygdala development in autism. Here, the authors characterize amygdala development across childhood in autistic children with and without traditional DSM forms of anxiety and anxieties distinctly related to autism. Longitudinal magnetic resonance imaging scans were acquired at up to four time points for 71 autistic and 55 typically developing (TD) children (∼2.5–12 years, 411 time points). Traditional DSM anxiety and anxieties distinctly related to autism were assessed at study time 4 (∼8–12 years) using a diagnostic interview tailored to autism: the Anxiety Disorders Interview Schedule-IV with the Autism Spectrum Addendum. Mixed-effects models were used to test group differences at study time 1 (3.18 years) and time 4 (11.36 years) and developmental differences (age-by-group interactions) in right and left amygdala volume between autistic children with and without DSM or autism-distinct anxieties and TD children. Autistic children with DSM anxiety had significantly larger right amygdala volumes than TD children at both study time 1 (5.10% increase) and time 4 (6.11% increase). Autistic children with autism-distinct anxieties had significantly slower right amygdala growth than TD, autism–no anxiety, and autism–DSM anxiety groups and smaller right amygdala volumes at time 4 than the autism–no anxiety (−8.13% decrease) and autism–DSM anxiety (−12.05% decrease) groups. Disparate amygdala volumes and developmental trajectories between DSM and autism-distinct forms of anxiety suggest different biological underpinnings for these common, co-occurring conditions in autism. [ABSTRACT FROM AUTHOR]