21922
Attention-Deficit/Hyperactivity Disorder Is Common in Autism Spectrum Disorder and Negatively Affects the Clinical Presentation
The co-existence of autism spectrum disorder (ASD) and attention-deficit/hyperactivity disorder (ADHD) has recently been supported by the DSM 5. The prevalence rate of ADHD symptoms within ASD populations has been reported to be between 16-50%, significantly more than in the general population (7-10%). The impact of having ASD and ADHD on the severity of the clinical presentation has been investigated in only a few studies. More severe ASD symptoms, emotional instability, poorer adaptive skills and poor academic achievements positively correlated with the existence of ADHD symptoms.
Objectives:
1. To assess the rate of ADHD symptoms in a population diagnosed with ASD
2. To compare the clinical presentation in a subgroup with only ASD diagnosis to a subgroup with ASD and ADHD symptoms.
Methods:
The study included 155 participants, diagnosed with ASD, age range 4:0-10:8y (M=6:7; SD=20.8m) and with male:female ratio of 6.4:1. All the participants underwent comprehensive medical, cognitive and behavioral assessments using standardized tests. Autism symptom severity was measured using the Autism Diagnostic Observation Schedule calibrated severity scales (ADOS CSS). ADHD symptom severity was measured using the Conners Teacher ADHD rating scale-the long form (CRS-R). Standard scores > 60 on any of the different DSM-IV ADHD subscales are considered significant for ADHD symptoms.
Results:
Using the Teacher CRS-R, of the ASD population, a score > 60 was noted for 66% on the DSM ADHD total score subscale, for 66.5% on the DSM Inattention subscale and for 46.5% on the DSM Hyperactive–Impulsive subscale.
We then divided the entire ASD group into two subgroups, one without ADHD symptoms (ASD-ADHD) (n=75; mean age=6:3y)) and the second with ADHD symptoms (ASD+ADHD) (n=80; mean age=6:5y). The two subgroups were compared for age, sex, autism severity, cognitive level and anxiety symptoms. The two subgroups were not significantly different in age. A trend for lower male:female ratio (relatively more girls) was observed for the subgroup ASD+ADHD (4.7:1) compared to the subgroup ASD-ADHD (9.7:1) (p=.7).
Looking at cognitive measures, the ASD+ADHD subgroup had significantly lower IQ scores (M=86.3, SD=19.1) than the subgroup ASD-ADHD (M=93.0, SD=19.4) (p<.05). Examining the verbal and non-verbal IQ scores revealed that only for the non-verbal IQ scores, the ASD+ADHD subgroup (M=95.7, SD=18.9) had significantly lower scores than the ASD-ADHD subgroup (M=105.0, SD=18.9) (p<.05).
A high prevalence of anxiety symptoms, measured by the Anxiety subscale scores of the CRS-R, was noted for the two subgroups. The prevalence was significantly higher for the subgroup ASD+ADHD (65.9%) than for the subgroup ASD-ADHD (35.6%) (p<.001). Comparison of autism severity using the ADOS-CSS measure revealed no significant difference between the two studied subgroups.
Conclusions:
A high rate of ADHD symptoms was noted in ASD in comparison with the general population. In ASD with ADHD, inattention was the most commonly reported symptom. The clinical presentation in ASD with ADHD is characterized by lower cognitive ability and more anxiety symptoms; however autism severity is not affected. In light of the negative effects of ADHD on the clinical presentation, it is highly important to diagnose and treat ADHD in ASD.