Latent Structure of Combined Autistic and ADHD Symptoms in Clinical and General Population Samples: A Scoping Review

Abstract

Background: Many phenotypic studies have estimated the degree of comorbidity between Autism Spectrum Disorder (ASD) and Attention Deficit Hyperactivity Disorder (ADHD), but few have examined the latent, or unobserved, structure of combined ASD and ADHD symptoms. This is an important perquisite toward better understanding the overlap between ASD and ADHD.Methods: We conducted a scoping review of studies that examined the factor or latent class structure of ASD and ADHD symptoms within the same clinical or general population sample.Results: Eight studies met final inclusion criteria. Four factor analysis studies found that ASD and ADHD domains loaded separately and one found that some ASD and ADHD domains loaded together. In the three latent class studies, there were evidence of profiles with high levels of co-occurring ASD and ADHD symptoms.Conclusions: Our scoping review provides some evidence of phenotypic overlap between ASD and ADHD at the latent, or unobserved, level, particularly when using a “person-centered” (latent class analysis) vs. a “variable-centered” (factor analysis) approach.

Do ASD and ADHD Have Distinct Executive Function Deficits? A Systematic Review and Meta-Analysis of Direct Comparison Studies

“…Some studies which included a comorbid group found greater deficits in the comorbid group compared to the ASD, ADHD and typically developing groups (Antshel & Russo, 2019;Craig et al, 2016;Hwang-Gu et al, 2019). These studies do not clarify whether EFs are associated with ASD or ADHD or whether the comorbid group represents a distinct diagnostic entity (Caron & Rutter, 1991;Krakowski et al, 2021). Studies in which ADHD and ASD traits were controlled indicate that, at least response inhibition and response variability, may be more strongly associated with ADHD than with ASD traits (Karalunas et al, 2018;Schachar et al, 2022).…”

The distribution of parent‐reported attention‐deficit/hyperactivity disorder and subclinical autistic traits in children with and without an ADHD diagnosis

“…Methodological differences in recruitment, measurement, and analysis mean that many results are only comparable to findings derived from analytical techniques of the same class. For example, Krakowski et al (2021) highlighted in their scoping review that the latent class studies often identified more phenotypic overlap between autism and ADHD, whereas factor analytic studies tended to support distinct 'autism' and 'ADHD' factors. A key recommendation from their review was for future studies to employ statistical methods that combine multiple techniques together, such as factor mixture modelling (FMM).…”

“…Studies attempting to model the relationship between ADHD and autism have employed a variety of methods, including latent class analysis and factor analysis (Farhat et al., 2022 ; Krakowski et al., 2021 ). Methodological differences in recruitment, measurement, and analysis mean that many results are only comparable to findings derived from analytical techniques of the same class.…”

“…Secondary analyses of SCQ responses and 18 separate ADHD items revealed distinct social and inattentiveness factors, as well as a joint restricted/repetitive behaviour and hyperactivity factor. However, only one ADHD‐hyperactivity item loaded strongly onto this factor ( λ = 0.50; Costello & Osborne, 2005 ), so it is possible that this result was an artefact of exploratory factor analysis (Krakowski et al., 2021 ). There is an opportunity to further explore autistic traits in children with and without ADHD using FMM.…”