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De Francesco et al. J Transl Genet Genom 2024;8:102-18 Journal of Translational
DOI: 10.20517/jtgg.2023.51
Genetics and Genomics

Review Open Access

Exploring the comorbidity between
internalizing/externalizing dimensions and cognitive

disengagement syndrome through twin studies: a
narrative review

1
1
1,2
3
1
Stefano De Francesco , Cecilia Amico , Gaia De Giuli , Ludovica Giani , Corrado Fagnani , Emanuela
3
Medda , Simona Scaini 1,2
1
Child and Youth Lab, Sigmund Freud University, Milan 20144, Italy.
2
Child and Adolescent Unit, Italian Psychotherapy Clinics, Milan 20144, Italy.
3
Centre for Behavioural Sciences and Mental Health, Istituto Superiore di Sanità, Rome 00161, Italy.
Correspondence to: Simona Scaini, Child and Youth Lab, Sigmund Freud University, Ripa Di Porta Ticinese 77, Milan 20143, Italy.
E-mail: s.scaini@milano-sfu.it
How to cite this article: De Francesco S, Amico C, De Giuli G, Giani L, Fagnani C, Medda E, Scaini S. Exploring the comorbidity
between internalizing/externalizing dimensions and cognitive disengagement syndrome through twin studies: a narrative review.
J Transl Genet Genom 2024;8:102-18. https://dx.doi.org/10.20517/jtgg.2023.51
Received: 14 Nov 2023 First Decision: 24 Jan 2024 Revised: 9 Feb 2024 Accepted: 5 Mar 2024 Available online: 27 Mar 2024
Academic Editor: Richard Frye Copy Editor: Fangling Lan Production Editor: Fangling Lan

Abstract
Twin studies are cutting-edge design methodologies proper to behavioral genetics that aim to investigate how the
interplay between genetic and environmental factors can concur to explain individual differences in
psychopathology, temperamental traits, and behavior. This particular research design has been widely applied to
the study of comorbidity between internalizing (INT) and externalizing (EXT) symptoms, especially in childhood
and adolescence. Notably, the high co-occurrence of symptoms of both these diagnostic domains has led to the
hypothesis that at their basis, there might be one single latent common susceptibility factor, namely p factor. Twin
studies have contributed to marking a relevant turning point in this regard by highlighting the consistent genetic
nature of this factor. In light of these premises, the present narrative review aims to outline the path for future twin
studies in investigating the comorbidity between Cognitive Disengagement Syndrome (CDS) and INT-EXT
disorders, examining the evidence supporting this need and its clinical implications. Since CDS has not been
recognized as a stand-alone syndrome until very recently, research on this condition is still in its infancy and the
etiological factors at the basis of its comorbidity with INT-EXT are still unclear. Being aware of the causal factors
underneath the comorbidity between INT-EXT might pave the way for improving assessment diagnostic

© The Author(s) 2024. Open Access This article is licensed under a Creative Commons Attribution 4.0
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