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Autistic Traits in Children with ADHD Linked to High Risk of Psychopathology, Impaired Functioning

Key findings

  • In a longitudinal study, a clear majority of youth with ADHD who had autistic traits (ATs) at baseline continued to manifest them at 10- or 11-year follow-up
  • ATs at baseline predicted a more compromised clinical course, including a greater burden of psychopathology and significantly more impaired psychosocial, academic and neurocognitive functioning compared with youth who had ADHD but no ATs
  • These findings strongly support the utility of the Child Behavior Checklist in identifying the sizable minority of youth with ADHD who are at high risk of poor functioning in adulthood

Symptoms of autistic spectrum disorder (ASD) and attention deficit hyperactivity disorder (ADHD) often co-occur. In addition, there's emerging evidence that autistic traits (ATs) are associated with significant morbidity and dysfunction in youth with ADHD, even though they don't meet the diagnostic threshold for ASD.

Joseph Biederman, MD, chief of the Pediatric Psychopharmacology & Adult ADHD Program at Massachusetts General Hospital, and colleagues previously reported in the Scandinavian Journal of Child and Adolescent Psychiatry and Psychology that ATs are present in 18% of youth with ADHD, a significantly higher proportion than in youth without ADHD. The presence of ATs was associated with compromised function in school, social activities and other situations. However, that research was cross-sectional, so it wasn't known whether ATs persist or have prognostic utility.

Now, Dr. Biederman, Gagan Joshi, MD, director of the Autism Spectrum Disorder Program in Pediatric Psychopharmacology and medical director of the Alan & Lorraine Bressler Program for Autism Spectrum Disorder, and colleagues have conducted a decade-long follow-up study on children with and without ADHD. In European Child & Adolescent Psychiatry, they report that ATs in children with ADHD do predict a very high risk of psychopathology and impaired interpersonal, educational and neuropsychological functioning. Fortunately, clinicians should be able to identify such children often by asking an adult caregiver to complete an evaluation.

Study Design

The researchers derived their sample from two longitudinal case–control studies of children with and without ADHD, conducted by Dr. Biederman and colleagues, including one focused on girls published in Biological Psychiatry and on focused on boys published in Psychiatry Research with and without ADHD. A diagnosis of autism was an exclusion criterion. At baseline, the subjects were 6 to 17 years old.

An adult caregiver for each subject completed the 1991 version of the Child Behavior Checklist (CBCL) for Ages 4–18. It has eight clinical subscales (anxious/depressed, withdrawn/depressed, somatic complaints, social problems, thought problems, attention problems, rule-breaking behavior and aggressive behavior) and four competence subscales (school, activities, social and total).

The CBCL does not directly assess for ATs. Rather, the researchers defined the presence of ATs at baseline as an aggregate score of ≥195 on the withdrawn/depressed, social problems and thought problems subscales (CBCL-AT score). Subjects who had ADHD and ATs at baseline were considered to have persistent ATs at follow-up if they had an aggregate score of ≥180 on the three subscales.

Other assessments included:

  • Structured Clinical Interview for DSM-IV (indirect interviews with adult caregivers and direct interviews with subjects ≥12 years old)
  • Modules from the Kiddie Schedule for Affective Disorder and Schizophrenia for Children (for subjects ≤18 years old)
  • DSM-IV Global Assessment of Functioning (GAF)
  • Social Adjustment Inventory for Children and Adolescents (SAICA)
  • Placement in special classes, extra tutoring or repeated grades
  • Wechsler Adult Intelligence Scale (WAIS) or Wechsler Intelligence Scale for Children (WISC)
  • Wide Range Achievement Test, which measures achievement in mathematics and reading

Stability of Autistic Traits

At baseline, the subjects were categorized as:

  • Control subjects, n=227
  • ADHD subjects without AT (ADHD−AT), n=198
  • ADHD subjects with AT (ADHD+AT), n=49

The girls were reassessed after five years and 11 years, and the boys were reassessed after one year, four years and 10 years. 80% of controls, 79% of ADHD−AT subjects and 69% of ADHD+AT subjects returned for the 10- or 11-year follow-up. At that time, 19 (83%) of the ADHD+AT subjects had a persistent AT profile based on a CBCL-AT score ≥180.

Patterns of Psychiatric Comorbidity

At the 10-/11-year follow-up, the average number of lifetime psychiatric comorbidities was significantly higher among ADHD+AT subjects (9.0) than ADHD−AT subjects (6.5) or controls (2.7).

Specifically, compared with the controls and ADHD−AT subjects, the ADHD+AT subjects were at significantly higher risk of oppositional defiant disorder, conduct disorder, antisocial personality disorder, ≥2 anxiety disorders, bipolar disorder and major depressive disorder. Subjects with ADHD+AT also showed significantly more impairment on all subscales of the CBCL.

Among the ADHD+AT subjects, the risk of oppositional defiant disorder, anxiety disorders, bipolar disorder and major depressive disorder was higher before puberty and markedly lower in the post-pubertal years. This finding was in significant contrast with ADHD−AT subjects and controls, whose lifetime risk of major psychopathology was equally high in the pre- and post-pubertal years.

Psychosocial Functioning

Compared with the controls and ADHD−AT subjects, ADHD+AT subjects had significantly more impaired scores in the SAICA domains of spare time problems, activities with peers and problems with peers. They also had significantly more impaired scores on the CBCL social competence scale. Compared with ADHD−AT subjects, ADHD+AT subjects had significantly more impaired lifetime GAF scores.

Academic and Neurocognitive Functioning

ADHD+AT subjects were significantly more likely than ADHD−AT subjects to have been placed in a special class. They were also less likely to complete high school, although the difference was not statistically significant.

Compared with ADHD−AT subjects, ADHD+AT subjects were significantly more impaired on the WAIS/WISC arithmetic subscale and the freedom from distractibility factor.

Clinical Applications

  • When taking care of a child with ADHD, assess for ATs by asking an adult caregiver to complete the CBCL, a widely available, inexpensive, paper-and-pencil scale with excellent psychometric properties
  • Don't expect patients to outgrow the presence of ATs. Upon recognizing them, encourage families to seek specific therapeutic interventions as early as possible
  • Counsel families that children with ADHD and ATs are at high risk for the onset of major psychiatric disorders before puberty, but the risk is substantially reduced in adolescence

of youth with ADHD have autistic traits

Learn more about the Pediatric Psychopharmacology & Adult ADHD Program

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