Cognitive task performances as biomarkers & candidate endophenotypes in childhood neurodevelopmental disorders : ADHD & autism

• Main Author: Azadi Sohi, Bahare
• Published: King's College London (University of London) 2012
• Subjects: 616.85
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.628103

Autism spectrum disorder (ASD) and Attention Deficit Hyperactivity Disorder (ADHD) are both defined on the basis of behavioural impairments and there is no informative biological test available for the diagnosis of the two disorders yet. The current diagnostic criteria adopt hierarchical approach and preclude the diagnoses of ADHD and ASD in an individual. The thesis investigated whether ASD and ADHD could be discriminated based on their neuropsychological profiles. Moreover, the study explored the cognitive profile of the comorbid ASD-ADHD group. Finally, the thesis assessed whether the biomarkers represent putative endophenotype. The findings suggested that even though the core diagnostic criteria of ADHD and ASD are entirely different, they can co-occur possibly due to shared risk. The neuropsychological data revealed that the poor inhibitory control and premature style of responding appeared to be candidate biomarkers that showed some differentiation between ADHD and ASD. Whereas, weak central coherence style as observed by a disregard for sentence context and impairment in response monitoring were in common to both disorders. Comorbidity was not associated with a more impaired cognitive profile than the pure groups. The comorbid ASD-ADHD group showed a response inhibition deficit and a premature style of responding similar to the ADHD group; and relatively poor understanding of the stories with social content similar to the ASD group. In addition, similar to both groups, they showed impairments of response monitoring and the weak coherence style in verbal domain, which suggests similar neuropsychological correlates. The study opened up an avenue for future endophenotype research by showing antisaccade correction rate and saccade amplitude to meet the co-familiarity criterion for a broad endophenotype that is shared across ASD and ADHD. The study has implication for diagnosis and treatment of the two disorders and their comorbidity, and suggests that the comorbid ASD-ADHD could be a fruitful candidate for future research.