Emotional Dysregulation and Cognitive Disengagement Syndrome: Exploring Their Relationship Through the Lens of Twin Studies  
[PERSON]  
1 Child & Youth Lab, Sigmund Freud University of Milan, Via Ripa di Porta Ticinese 77, 20143 Milan, Italy; 1  
[PERSON]  
1 Child & Youth Lab, Sigmund Freud University of Milan, Via Ripa di Porta Ticinese 77, 20143 Milan, Italy; 1  
[PERSON]  
1 Child & Youth Lab, Sigmund Freud University of Milan, Via Ripa di Porta Ticinese 77, 20143 Milan, Italy; 1  
[PERSON]  
1 Child & Youth Lab, Sigmund Freud University of Milan, Via Ripa di Porta Ticinese 77, 20143 Milan, Italy; 1  
[PERSON]  
3 Department of Psychology, University of Bilkent, 06800 Cankaya, Ankara, Turkey; [EMAIL_ADDRESS]  
[PERSON]  
1 Child & Youth Lab, Sigmund Freud University of Milan, Via Ripa di Porta Ticinese 77, 20143 Milan, Italy; 1  
[PERSON]  
4 Department of Life Sciences, University of Trieste, [PERSON], 2, 34128 Trieste, Italy; [EMAIL_ADDRESS]  
[PERSON]  
1 Child & Youth Lab, Sigmund Freud University of Milan, Via Ripa di Porta Ticinese 77, 20143 Milan, Italy; 1  
and [PERSON]  
1 Child & Youth Lab, Sigmund Freud University of Milan, Via Ripa di Porta Ticinese 77, 20143 Milan, Italy; 1  
Footnote 1: email: [EMAIL_ADDRESS]  
Footnote 2: email: [EMAIL_ADDRESS]  
Footnote 3: email: [EMAIL_ADDRESS]  
Footnote 4: email: [EMAIL_ADDRESS]  
Footnote 5: email: [EMAIL_ADDRESS]  
Footnote 6: email: dj.forresi  
Interest in studying this condition among researchers and clinicians emerged in the late 1980s, following factor analytic studies that began differentiating CDS from the inattentive subtype of Attention-Deficit/Hyperactivity Disorder (ADHD) [1]. Initially, CDS was regarded as synonymous with the inattentive presentation of ADHD [5]. However, later research has increasingly emphasized the distinctiveness of these two constructs, and CDS is now recognized as a separate nosological entity, although it has not yet been included in current diagnostic classification systems [6]. In recent years, an increasing body of research has examined the association between Cognitive Disengagement Syndrome (CDS) and Emotional Dysregulation (ED). ED is characterized by heightened emotional reactivity, including pronounced irritability, frequent outbursts, mood instability, low frustration tolerance, and increased emotional sensitivity [7]. The growing interest in investigating these two phenotypes together arises from their transdiagnostic nature and their shared associations with both internalizing and externalizing disorders [4,8]. However, despite promising findings, research on their co-occurrence remains in its early stages, and current evidence raises more questions than it answers, particularly regarding the etiological mechanisms underlying this comorbidity.  
Given these premises, it is crucial to emphasize the importance of addressing this issue through the framework of Quantitative Genetics, which provides a powerful methodological approach for disentangling the genetic and environmental factors underlying psychological disorders [9]. Quantitative genetic studies, particularly twin studies, are widely utilized in developmental psychopathology research and have substantially advanced our understanding of the etiological foundations of comorbidities between phenotypes [9].  
In light of the above, this review aims to explore the potential value of twin studies in elucidating the genetic and environmental foundations of the co-occurrence of ED and CDS manifestations. Following an introductory overview of research designs in quantitative behavioral genetics, the review will examine the core characteristics of both CDS and ED, along with the existing literature on their co-occurrence. The discussion will then highlight the importance of employing twin study designs to deepen our understanding of the comorbidity between these two phenomena.