Boys with fragile X syndrome (FXS) who experience negative emotions such as anger and fear up to preschool age are more prone to develop anxiety, a new study suggests.
The study, “Early negative affect in males and females with fragile X syndrome: implications for anxiety and autism,” was published in the Journal of Neurodevelopmental Disorders and was conducted by University of South Carolina researchers.
FXS is the most common genetic cause of autism and intellectual disability. The prevalence of autism spectrum disorder (ASD), an umbrella term for autistic behaviors, ranges from 50–75% in males and reaches 25% of females with fragile X. Anxiety also is common, and is present in 86% of males and 77% of females with fragile X.
Early predictors of anxiety and ASD in fragile X are lacking. Also unknown is whether the prevalence of these comorbidities is different between males and females with fragile X.
Negative affect is a concept that includes fear, sadness, frustration, and difficulty regulating emotions, involving a generally negative way of experiencing the world. It is used in clinics as a predictor of anxiety and ASD for infants and toddlers.
Seeking to assess the prevalence of negative affect and whether its impact is different in boys and girls with fragile X, researchers followed a total of 185 children from the age of 6 months to 60 months (5 years), of whom 116 have fragile X (75% male) and 69 with typical development (79.7% male).
The study also intended to explore whether negative affect could predict anxiety and ASD in children with fragile X.
Negative affect was measured using the Rothbart Temperament Questionnaires, one of the most-used measures for this purpose in infancy and childhood. The questionnaires are answered by parents and include three different sets according to the child’s age: the Infant Behavior Questionnaire-Revised for infants between 6 and 18 months; the Early Childhood Behavior Questionnaire for children between 18–36 months; and the Children’s Behavior Questionnaire for children 36–60 months.
The Spence Children’s Anxiety Scale for Parents (SCAS-P) was used to measure anxiety, and the Autism Diagnostic Observation Schedule, Second Edition (ADOS-2) was used to explore ASD. The SCAS-P score has an average of 50, and higher scores represent more anxiety symptoms. The ADOS-2 scoring system ranges from 1 to 10, and higher values reflect more severe ASD symptoms.
The Mullen Scales of Early Learning (MSEL) was used to measure development level, and spans motor and visual domains, as well as language skills.
The analysis revealed that negative affect increased from infancy through preschool in both controls and children with fragile X. However, the increases were steeper in children with fragile X, with lower levels than in the controls from 6 to 36 months of age, followed by increases to similar levels of controls from 36 months onward.
This atypical variation in fragile X, the scientists observed, was largely driven by sex, specifically males. After showing lower levels than girls during infancy, boys with fragile X showed steep increases across the toddler and preschool years. In contrast, girls showed a flatter trajectory throughout the study.
“Male infants with FXS displayed lower negative affect than female infants with FXS at 6 months, equivalent levels at 12 months, and higher negative affect by 36 months,” the investigators wrote.
The smaller increase in girls compared to boys may reflect their milder symptoms, the scientists said.
Of note, no gender differences were seen in the control group.
Increased negative affect predicted anxiety symptoms in boys, but not in girls. In turn, negative affect was not linked with ASD in fragile X, irrespective of gender.
Overall, these results suggest that “temperamental negative affect can be an important early marker for anxiety in young children with FXS,” the researchers wrote. Also, they “provide opportunities for the pursuit of an important target for early detection and intervention.”
These findings also show that “including both males and females in FXS research can enhance our understanding of the unique vulnerabilities and needs of either sex,” they added.
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