Abstract
Background: Current global estimates suggest the proportion of the population with autism spectrum disorder (ASD) who have intellectual disability (ID) is approximately 50%. Our objective was to ascertain the existence of selection bias due to under-inclusion of populations with ID across all fields of autism research. A sub-goal was to evaluate inconsistencies in reporting of findings. Methods: This review covers all original research published in 2016 in autism-specific journals with an impact factor greater than 3. Across 301 included studies, 100,245 participants had ASD. A random effects meta-analysis was used to estimate the proportion of participants without ID. Selection bias was defined as where more than 75% of participants did not have ID. Results: Meta-analysis estimated 94% of all participants identified as being on the autism spectrum in the studies reviewed did not have ID (95% CI 0.91-0.97). Eight out of ten studies demonstrated selection bias against participants with ID. The reporting of participant characteristics was generally poor: information about participants' intellectual ability was absent in 38% of studies (n = 114). Where there was selection bias on ID, only 31% of studies mentioned lack of generalisability as a limitation. Conclusions: We found selection bias against ID throughout all fields of autism research. We recommend transparent reporting about ID and strategies for inclusion for this much marginalised group.
Original language | English |
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Article number | 9 |
Journal | Molecular Autism |
Volume | 10 |
Issue number | 1 |
DOIs | |
Publication status | Published - 1 Mar 2019 |
Bibliographical note
Funding Information:We would like to thank to Darren Moore, Hateem Rafeeque, Delphine Jacobs and Ruth Gwernan-Jones for their help and advice on the study, and the generous support of the Wellcome Trust, Grant ref.: 108676/Z/1 SfZ.
Funding Information:
This work was supported by a Wellcome Trust Investigator Award, Grant ref.: 108676/Z/1 SfZ. The funders had no role in development of the work.
Publisher Copyright:
© 2019 The Author(s).
Copyright:
Copyright 2019 Elsevier B.V., All rights reserved.
Funding
We would like to thank to Darren Moore, Hateem Rafeeque, Delphine Jacobs and Ruth Gwernan-Jones for their help and advice on the study, and the generous support of the Wellcome Trust, Grant ref.: 108676/Z/1 SfZ. This work was supported by a Wellcome Trust Investigator Award, Grant ref.: 108676/Z/1 SfZ. The funders had no role in development of the work.
Keywords
- Autism
- Autism spectrum disorder
- Intellectual disability
- Nosology
- Selection bias
ASJC Scopus subject areas
- Molecular Biology
- Developmental Neuroscience
- Developmental Biology
- Psychiatry and Mental health