In the 0–2 years age group, we found no evidence of autistic behaviors, opposite provocative disorders, attention deficit/hyperactivity disorders nor externalizing or internalizing symptoms. However, consistent with the literature, we observed sleep disorders in 25% of cases (4 out of 16) [
7] and mastication dysfunction in 12.5% of children (2 out of 16) [
6]. Between 2 and 3 years of age, ODD behavior and anxiety arise. Between 4 and 5 years, ODD behavior is present, hyperactivity and inattention are more relevant and anxiety has a high level of expressiveness. Between 6 and 10 years, ODD behavior and anxiety predominate, hyperactivity and inattention persist and increases the presence of mood alteration. From 11 years old, externalizing-like behavior decreases while the prevalence of anxiety and depression symptoms increases.
Compared with the mild incidence of psychopathology described in literature, the percentage of risk factors of this study is high: 94% of the sample. In [
19], Visootsak et al. estimated the incidence of psychopathological characteristics in DS in a percentage between 20 and 40% of affected subjects [
19]. The study by Van Gameren-Oosterom et al. on 513 adolescent patients with DS showed a percentage of behavior problems of 51% [
16,
17]. The high prevalence of psychopathological risk factors in our sample suggests the need for accurate neuropsychiatric monitoring over the life span, also to identify predictors of psychopathology in the long term [
11,
12,
18]. Moreover, in the studies exploring the cognitive and behavioral characteristics of subjects with DS there is much more attention to the analysis of cognitive and neuropsychological functions than those related to emotional and behavioral functioning. In [
10], Grieco et al., highlighted the need of more studies to address emotional, behavioral and psychopathological aspects [
10]. The data emerged from this work, therefore, suggest a high incidence of psychopathological risk, in spite of literature data that report only a moderate incidence of psychopathology. As reported in the literature, in this sample no significant psychopathological risk factors were detected in the first 2 years of life; however, during this age range, as emerged during the neuropsychiatric examination, a moderate impairment in emotional and behavioral regulation can occur and intolerance to frustration. This could be explained, in part, in relation to the global maturation process delay. These early childhood features should be explored, in our opinion, in order to evaluate their long-term impact [
9]. In this sample, between 4 and 5 years of age, ODD behavior and anxiety dominate. The association, in DS children, between ODD and anxiety behavior suggests the possibility that dysfunctional behavior is reactive to an emotional dimension marked by insecurity and anxiety, poorly mentalized and regulated, also because of ID. Moreover, the difficulty to express their emotions facilitates the presence of oppositional and impulsive behaviors, also as a dysfunctional and unconscious way for controlling the environment, or for shifting the focus on their behavior rather than on the difficulties underlying them. In this age range, the greater relevance of symptoms of ADHD may be partly explained by these factors: with growth, the role of cognitive and executive functions in controlling mental and behavioral processes becomes more complex and crucial in defining a good functioning from a deficit functional level. The processes of attention, concentration and motivation mature, allowing progressively greater stability and greater control capability. A delay in maturation of these processes, as often occurred in DS, can play a key role in the development of symptoms of inattention and hyperactivity; moreover, with the growth and the schooling, environmental demands increase, so the impairment is more evident. Between 6 and 10 years the presence of mood alteration increases: this is in part correlated to the psychological growth, which, especially in DS subjects with better cognitive competence, involves a greater awareness of their condition and of the related difficulties. Moreover, at this age, the perception of themselves and other individual characteristics begins to develop; this can, in general, make the peer group less inclusive toward a child with disability, making integration and social contacts more difficult. These elements can undoubtedly have an impact on mood and on behavior, leading at the increase of depressive symptoms. In this sample, 7 subjects (7%) have a cut-off overcoming (score > 30) for the presence of autistic behaviors (ASD) at the CARS-T rating scale, confirmed at the neuropsychiatric examination. DS subjects with autism symptoms have peculiar features: increased stereotypes, higher level of anxiety, and increased adaptive impairment, if compared to typical autism. The presence of these specific characteristics in the subjects of this sample, consistent with the hypothesis of a specific autistic phenotype in Down’s syndrome, is an important preliminary data to be further analyzed.
This element is, in our view, very important, because it underlines the importance of using specific screening tools to identify specific psychopathological features, otherwise unidentified or merely attributed to secondary aspects of mental retardation. The diagnosis of specific traits of autism in DS is relevant from a clinical point of view, but very complex. Dressler et al., in a 2011 study on adaptive behavior of subjects with DS and autism, showed how autism in DS is often underestimated in the clinical context, because it is often assimilated to characteristics related to ID [
2]. As highlighted in this paper, the need to screen specifically comorbidity between Down syndrome and Autism is relevant to a clinical and therapeutic point of view.
In our sample, the degree of intellectual disability (moderate vs mild intellectual disability) was not associated with increased risk of behavioral disorders (Chi2 1.2; p 0.2). No patient with severe intellectual disability was present in our cohoort.
Hence, in this study, the risk of psychopathology is independent of the degree of intellectual disability.