The opposite end of the attention deficit hyperactivity disorder continuum: genetic and environmental aetiologies of extremely low ADHD traits.

Background: Although attention deficit hyperactivity disorder (ADHD) is thought to reflect a continuously distributed quantitative trait, it is assessed through binary diagnosis or skewed measures biased towards its high, symptomatic extreme. A growing trend is to study the positive tail of normally distributed traits, a promising avenue, for example, to study high intelligence to increase power for gene-hunting for intelligence. However, the emergence of such a 'positive genetics' model has been tempered for ADHD due to poor phenotypic resolution at the low extreme.

How 'core' are motor timing difficulties in ADHD? A latent class comparison of pure and comorbid ADHD classes.

Unlabelled: Children with attention-deficit/hyperactivity disorder (ADHD) have motor timing difficulties. This study examined whether affected motor timing accuracy and variability are specific for ADHD, or that comorbidity with autism spectrum disorders (ASD) contributes to these motor timing difficulties. An 80-trial motor timing task measuring accuracy (μ), variability (σ) and infrequent long response times (τ) in estimating a 1-s interval was administered to 283 children and adolescents (8-17 years) from both a clinic and population based sample.

Do High and Low Extremes of ADHD and ASD Trait Continua Represent Maladaptive Behavioral and Cognitive Outcomes? A Population-Based Study.

Objective: Attention deficit hyperactivity disorder (ADHD) and autism spectrum disorders (ASD) are thought to reflect the high, symptomatic extreme of quantitative trait continua. However, extreme deviations in either direction on disorder continua, high and low, may both represent maladaptive behavioral and cognitive outcomes. We aimed to test this hypothesis.

Homogeneous Combinations of ASD-ADHD Traits and Their Cognitive and Behavioral Correlates in a Population-Based Sample.

Objective: Autism Spectrum Disorders (ASD) and ADHD are assumed to be the extreme manifestations of continuous heterogeneous traits that frequently co-occur. This study aims to identify subgroups of children with distinct ASD-ADHD trait profiles in the general population, using measures sensitive across both trait continua, and show how these subgroups differ in cognitive functioning.

Method: We examined 378 children (6-13 years) from a population-based sample.

Recognition of facial emotion and affective prosody in children with ASD (+ADHD) and their unaffected siblings.

Autism is a highly heritable and clinically heterogeneous neuropsychiatric disorder that frequently co-occurs with other psychopathologies, such as attention-deficit/hyperactivity disorder (ADHD). An approach to parse heterogeneity is by forming more homogeneous subgroups of autism spectrum disorder (ASD) patients based on their underlying, heritable cognitive vulnerabilities (endophenotypes). Emotion recognition is a likely endophenotypic candidate for ASD and possibly for ADHD.

Are autism spectrum disorder and attention-deficit/hyperactivity disorder different manifestations of one overarching disorder? Cognitive and symptom evidence from a clinical and population-based sample.

Objective: Autism spectrum disorders (ASD) and attention-deficit/hyperactivity disorder (ADHD) frequently co-occur. Given the heterogeneity of both disorders, several more homogeneous ASD-ADHD comorbidity subgroups may exist. The current study examined whether such subgroups exist, and whether their overlap or distinctiveness in associated comorbid symptoms and cognitive profiles gives support for a gradient overarching disorder hypothesis or a separate disorders hypothesis.