Gastrointestinal Problems Are Associated with Increased Repetitive Behaviors but Not Social Communication Difficulties in Young Children with Autism

Background: Gastrointestinal (GI) symptoms have a well-established relationship with psychosocial problems and mood disorders in the general population, with GI symptoms demonstrating connections to difficulties with internalizing behaviors, depression, phobias, social skills, and adaptive behaviors. Some of these features are present in individuals with autism spectrum disorder (ASD). Individuals with ASD are more likely to experience a range of GI problems than typically developing (TD) individuals, including chronic diarrhea, constipation, food allergies, and abdominal pain. These symptoms have been associated with higher levels of irritability and aggressive behavior, but less is known about their relationship with core autism symptoms.

Objectives: To explore the relationship between GI symptom severity and core ASD symptoms while accounting for associated symptoms in a sample of children with ASD.

Methods: Participants were 176 children (140 males and 36 females) with ASD based on DSM-5 diagnosis, informed by the Autism Diagnostic Observation Schedule, Second Edition (ADOS-2) and ADI-R. Participants were 2 to 7 years old (M=64.9 months, SD=19.5). Mean Full Scale IQ (FSIQ) was 69.0 (SD=20.9). Autism symptom severity was measured with ADOS-2, Pervasive Developmental Disorder-Behavior Inventory (PDDBI), Vineland Adaptive Behavior Scales, Third Edition (VABS-3), and Clinical Global Impression Scale-Severity (CGI-S). Associated symptoms, including irritability, aggressiveness, and specific fears, were measured with Aberrant Behavior Checklist-Community (ABC) and PDDBI. Severity of GI problems was measured using PedsQL-Gastrointestinal Symptoms Inventory (PedsQL-GI). First, we examined zero-order correlations using univariate models for each ASD symptom, associated symptom domain, and overall GI symptoms. Second, we ran multivariable models exploring the relationship between GI problems and ASD symptoms while accounting for each associated symptom domain individually.

Results: A large majority (93.2%) of the sample had at least one reported GI problem, and 88.1% of participants had more than one GI problem. Various types of GI symptoms were experienced in the sample. Constipation, food limits, gas/bloating, and stomach pain were the most commonly reported symptoms. In the univariate regression models, Irritability; Aggressiveness; Specific Fears; Repetitive, Ritualistic, and Pragmatic Problems; Autism Composite Score; Stereotypy; and Inappropriate Speech were associated with PedsQL-GI Composite Score. In the multivariable models, after accounting for associated symptoms (i.e., Irritability, Aggressiveness, or Specific Fears), Repetitive, Ritualistic, and Pragmatic Problems (p-values ranged from 0.028 to 0.056) and Stereotypies (p-values ranged from 0.014 to 0.040) were significantly associated with GI symptom severity. Increased severity of associated symptoms was associated with increased GI symptom severity. Social and communication measures from the PDDBI and VABS-3 were not significantly associated with GI symptom severity after accounting for associated symptoms.

Conclusions: Our findings replicate a previously described association between irritability and aggression with GI symptoms. Building upon this, we sought to explore whether GI problems are correlated with core ASD symptoms after accounting for their relationship with associated symptoms, such as aggression, irritability, and fears. We found that repetitive behaviors, but not social or communication symptoms, are associated with GI symptom severity, even when accounting for emotional symptoms. This suggests that GI symptoms may exacerbate repetitive behaviors, or vice versa, independent from emotional symptoms.