Introduction
Autism spectrum disorder (ASD) and attention deficit hyperactivity disorder (ADHD) are two common neurodevelopmental disorders that often co-occur. Both disorders are associated with impairments in executive functions, such as planning, cognitive flexibility, and inhibitory control. However, it is not clear how the presence of ADHD affects the executive functioning of children with ASD. A recent study aimed to address this question by comparing the performance of four groups of children on three neuropsychological tests.
The study
The study involved 60 children aged between 5 and 10 years, who were divided into four groups: those with typical development (TD), those with high-functioning autism (ASD), those with autism and comorbid ADHD (ASD+ADHD), and those with only ADHD. The children were assessed on the following tests:
- Raven’s Colored Progressive Matrices (RPCM), which measures general intelligence and abstract reasoning.
- Tower of London (TOL), which measures planning ability and problem-solving skills.
- Modified Card Sorting Test (MCST), which measures cognitive flexibility and set-shifting ability.
The researchers also collected information on the children’s demographic characteristics, clinical diagnoses, and behavioral symptoms.
The results
The results showed that the ASD+ADHD group performed worse than the other groups on the TOL and the MCST, indicating that they had more difficulties in planning and cognitive flexibility. The ASD group also performed worse than the TD and the ADHD groups on the MCST, but not on the TOL. The ADHD group did not differ from the TD group on any of the tests. The RPCM scores did not differ significantly among the groups.
The researchers also found that the severity of ADHD symptoms, such as hyperactivity and impulsivity, was negatively correlated with the performance on the TOL and the MCST, but not on the RPCM. This suggests that ADHD symptoms may interfere with the executive functions that are required for these tasks. On the other hand, the severity of ASD symptoms, such as social communication and restricted interests, was not correlated with the performance on any of the tests.
The implications
The study provides evidence that children with ASD and comorbid ADHD have more severe impairments in executive functions than children with only ASD or only ADHD. This implies that the presence of ADHD may exacerbate the cognitive challenges that children with ASD face. The study also suggests that the executive functions that are affected by ADHD are different from those that are affected by ASD, and that these functions may be influenced by different factors, such as general intelligence, behavioral symptoms, and clinical diagnoses.
The findings of this study have important implications for the assessment and intervention of children with ASD and comorbid ADHD. The researchers recommend that clinicians should use comprehensive and sensitive neuropsychological tests to evaluate the executive functioning of these children, and to tailor the treatment plans according to their specific strengths and weaknesses. The researchers also suggest that future studies should explore the neural mechanisms and the developmental trajectories of executive functions in children with ASD and comorbid ADHD, as well as the effects of pharmacological and non-pharmacological interventions on these functions.
Faq
How did the researchers measure the general intelligence and abstract reasoning of the children?
The researchers measured the general intelligence and abstract reasoning of the children using the Raven’s Colored Progressive Matrices (RPCM), a nonverbal test that consists of 36 items. Each item presents a matrix of geometric patterns with one missing piece, and the child has to choose the correct piece from six options. The test measures the child’s ability to perceive and manipulate abstract relations, as well as the child’s fluid intelligence, which is the capacity to solve novel and complex problems.
How did the researchers measure the planning and problem-solving skills of the children?
The researchers measured the planning and problem-solving skills of the children using the Tower of London (TOL), a visuospatial test that consists of 12 items. Each item presents two pictures of three pegs with three colored balls on them, and the child has to move the balls from the initial state to the goal state in the minimum number of moves, following some rules. The test measures the child’s ability to plan, sequence, and execute a series of actions, as well as the child’s working memory and mental manipulation.
How did the researchers measure the cognitive flexibility and rule-switching ability of the children?
The researchers measured the cognitive flexibility and rule-switching ability of the children using the Modified Card Sorting Test (MCST), a verbal test that consists of 64 cards and four key cards. Each card has a picture of an object that varies in color, shape, and number, and the child has to sort the cards according to one of these dimensions, following the feedback from the examiner. The test measures the child’s ability to switch between different rules, categories, and strategies, as well as the child’s inhibitory control and error monitoring.
How did the researchers interpret and explain the results of the study?
The researchers interpreted and explained the results of the study using the theoretical framework of the dual-pathway model of ADHD (Sonuga-Barke, 2003). According to this model, ADHD is caused by two independent pathways: a delay aversion pathway and an executive dysfunction pathway. The delay aversion pathway reflects the preference for immediate rewards over delayed rewards, and the executive dysfunction pathway reflects the impairment in executive functions, such as response inhibition, sustained attention, and cognitive flexibility. The researchers suggested that the executive dysfunction pathway may be shared by both ASD and ADHD, whereas the delay aversion pathway may be specific to ADHD.
Source:
https://cab.unime.it/journals/index.php/JCDP/article/view/3700