Animal Models of Down Syndrome

Is intellectual disability a treatable feature of persons with Down syndrome? Researchers have made tremendous progress in the last 30 years, from creating the first mouse model of Down syndrome to completing the first major clinical trial for cognitive impairment in people with Down syndrome. Until recently, normalizing brain development and function seemed too lofty a goal, and indeed, even proposing a candidate therapy requires answering a number of difficult questions. How does trisomy 21, a molecular diagnosis, cause the clinical phenotypes of Down syndrome? When, where, and how do trisomic genes act to disrupt normal development and which genes are involved with which outcomes? Which brain regions and behaviors are most impaired? Is there an early developmental window of time during which treatments are most effective? This article discusses how animal models such as laboratory mice can be used to understand intellectual disability and to develop new treatments for cognitive impairment.

Development of Dementia, Including Assessment and Interventions

Adults with Down syndrome show premature aging with a high risk of developing dementia, specifically Alzheimer’s disease. Dementia in people with Down syndrome develops in addition to pre-existing intellectual disability, which poses difficulties in its diagnosis. Determining baseline function and conducting regular assessments are essential to detecting cognitive and functional decline. Comorbid conditions such as epilepsy and depression may also affect dementia presentation. As there is little evidence for effective pharmacological treatment of dementia in adults with Down syndrome, the identification of novel treatment targets is vital. In addition, a better understanding of the time course of the development of dementia will aid in better detection and monitoring of individuals showing early signs of cognitive decline. Early dementia-related changes may include prominent declines in behavior, personality disturbance, and early impairments in memory. Advances in neuroimaging and biomarker detection will further assist in understanding the time course of dementia development in people with Down syndrome.

Co-occurrence of Autism Spectrum Disorder and Down Syndrome

Autism spectrum disorder (ASD) refers to a heterogeneous condition characterized by deficits in social communication and the presence of restricted, repetitive, and stereotypic behaviors, interests, or activities. While some neurodevelopmental disorders have a well-established correlation with ASD, people continue to believe that because individuals with Down syndrome are characteristically perceived as affectionate and engaging, a diagnosis of ASD is contradictory. However, some people with Down syndrome indeed do meet diagnostic criteria for ASD and this chapter examines the research literature regarding Down syndrome and ASD, presenting information regarding the establishment of a diagnosis of ASD in individuals with Down syndrome and research techniques to understand the dual diagnosis of ASD and Down syndrome. Behavioral manifestations of ASD in Down syndrome are presented and research methodologies which address possible underlying mechanisms in Down syndrome and ASD are surveyed. Finally, the need for specification of behavioral profiles for individuals with a dual diagnosis of Down syndrome and ASD, in order to design and implement appropriate therapeutic interventions, is highlighted. Once a person with Down syndrome is diagnosed with ASD, he or she should automatically receive a combined treatment approach incorporating direct instruction, natural environment teaching, and incidental teaching. The manifestation of ASD in individuals with Down syndrome can shed light on our understanding of how ASD and intellectual disability are associated and what impact these diagnoses have on individuals and their families. This knowledge can help shape public policy and our research agenda in the areas of ASD, intellectual impairment, and Down syndrome.

From Transition Through Old Age: Caring for Adults With Down Syndrome

As adults with Down syndrome live longer lives, increased attention is being paid to their health, work, and living situations. In this chapter, we divide the adult years in Down syndrome into young adulthood—roughly from 20 through the late 40s—and older adulthood, from the late 40s until death in the late 50s or 60s. Many adults with Down syndrome are doing well during early adulthood, although concerns persist about their finding meaningful jobs, connecting to others in the community, and (sometimes) showing increased levels of depression. During later adulthood, changes emerge for many, including the onset of chronic “old-age” health problems during the 50s, as well as moving away from their parental homes (often occurring as late as the 40s). Despite 160 years of research on the syndrome, major gaps remain in our understanding of adulthood, especially concerning connections among the health, functioning, and work and residential status of the aging adult with Down syndrome, as well as the aging of their parents and their relationships with adult siblings.

Social-Emotional Competence in Down Syndrome

This chapter aims to synthesize historical and contemporary literature to provide an overarching understanding of social-emotional competence in individuals with Down syndrome, where social-emotional competence refers to the skills necessary to allow for successful social relationships, as well as the ability to regulate the experience and expression of emotions. Using the framework of Rose-Krasnor’s prism model, this chapter addresses each of the four components that underlie the development of social-emotional competence: self-regulation, social awareness, prosocial orientation, and social problem-solving. The development of each of these components is described for individuals with Down syndrome, and a description of the typical developmental trajectory is given for reference. The short-term and long-term implications of each component are also discussed, as they relate to the individual’s overall social-emotional competence. This overview aims to highlight what is known regarding social-emotional competence in individuals with Down syndrome, as well as to identify areas in which knowledge is lacking.

The Developing Brain in Down Syndrome

Research on the developing brain in persons with Down syndrome has grown in recent years thanks to advances in neuroimaging approaches that are safe for pediatric populations. This literature documents global reductions in total brain volume as well as specific alterations in both cortical and subcortical structures. These include reductions in hippocampal and cerebellar volumes (that are in excess of reduced total brain volume) as well as abnormalities in frontal and temporal lobe anatomy. Recent neuroimaging research has highlighted the importance of using fine-grained approaches to characterizing cortical and subcortical anatomy in persons with Down syndrome as well as interpreting these findings within the context of research on typical brain development. In the current review, we attempt to synthesize this literature from a developmental perspective. Our hope is that this developmental focus will lead to discoveries about the biological underpinnings and unfolding of the learning difficulties associated with Down syndrome.

Parenting the Child With Down Syndrome: Understanding—but Going Beyond—the “Down Syndrome Advantage”

Compared to parents of children with other types of intellectual disabilities, parents of children with Down syndrome experience less stress and more rewards, although this “Down syndrome advantage” mostly occurs compared to parents of children with autism and before groups are equated. Behaviorally, children with Down syndrome display more sociable interactional styles and baby-faced facial features, along with fewer instances of severe behavior problems. Demographically, parents of children with (versus without) Down syndrome average 5 years older when giving birth; parents are more often well educated, married, of higher socioeconomic status, and they likely provide these children greater financial and cultural resources. In most industrialized societies, rates of Down syndrome seem steady, with easily available, noninvasive prenatal testing counteracted by increasing numbers of women giving birth at older ages. Parenting children with Down syndrome relates to characteristics of children, their parents, and society, all of which intersect in important, underexplored ways.

Executive Function in Down Syndrome: Links to Adaptation and Treatment Implications

This chapter presents a review of existing research regarding the presentation of executive function in persons with Down syndrome. Contemporary scientific work regarding the development of executive function in persons with Down syndrome is reviewed, with an emphasis on profiles associated with childhood, adolescence, and adulthood. The valid assessment of executive function and methodological considerations are also discussed, including the importance of developing phenotype-sensitive and reliable measures of executive function that account for the broader profile of strengths and challenges associated with Down syndrome. Future areas of research are identified that can inform intervention approaches to target the development of goal-directed behavior and adaptation in this population.

Siblings’ Influence on the Development of Individuals with Down Syndrome

This chapter discusses the influences that siblings may have on developmental outcomes of children with Down syndrome including those related to cognition, language, self-regulation, social-emotional functioning, and identity formation. As there is very little research available that addresses sibling influences on individuals with Down syndrome, the literature related to sibling influence within sibships comprising typically developing children has been used to provide a starting point to the discussion. The influential roles of siblings may include teacher; model and social referent; friend and foe; contrast; and advocate, protector, and caregiver. The quality of the sibling relationship may also influence developmental outcomes. The few investigations that have been conducted suggest that siblings make an important contribution to developmental outcomes for individuals with Down syndrome. In conclusion, directions for future research are discussed.

Young Children with Down Syndrome: Mother-Child Dyadic Relationships

This chapter is focused on the mother-child dyadic relationship in families where a young child has Down syndrome. Because mothers enter into a relationship with a child within a particular context, a sociocultural perspective on parenting a child with Down syndrome promotes a deeper understanding of interaction in the mother-child dyad. Both the role of the family system, including positive parenting, and the contributions of the child’s attributes, especially temperament, are considered. Specific literature on the mother-child dyad is discussed, including maternal language input, the role of maternal directives during structured and unstructured tasks, and studies on autonomy-supportive parenting. Suggestions for future research include developing studies that focus on maternal strengths as well as conducting investigations that recognize the importance of the sociocultural context in which mother-child dyadic relationships are developed.