According to the dsm-5, an individual with an iq below 70 would be given a diagnosis of:

Prognosis

In children with severe ID, the prognosis is often evident by early childhood. Mild ID might not always be a lifelong disorder. Children might meet criteria for GDD at an early age, but later the disability can evolve into a more specific developmental disorder (communication disorder, autism, specific learning disability, or borderline normal intelligence). Others with a diagnosis of mild ID during their school years may develop sufficient adaptive behavior skills that they no longer fit the diagnosis as adolescents or young adults, or the effects of maturation and plasticity may result in children moving from one diagnostic category to another (from moderate to mild ID). Conversely, some children who have a diagnosis of a specific learning disability or communication disorder might not maintain their rate of cognitive growth and may fall into the range of ID over time.

The apparent higher prevalence of ID in low- and middle-income countries is of concern given the limitations in available resources.Community-based rehabilitation (CBR) is an effort promoted by WHO over the past 4 decades as a means of making use of existing community resources for persons with disabilities in low-income countries with the goal of increasing inclusion and participation within the community. CBR is now being implemented in >90 countries, although the efficacy of such programs has not been established.

The long-term outcome of persons with ID depends on the underlying cause, degree of cognitive and adaptive deficits, presence of associated medical and developmental impairments, capabilities of the families, and school and community supports, services, and training provided to the child and family (Table 53.7). As adults, many persons with mild ID are capable of gaining economic and social independence with functional literacy, but they may need periodic supervision (especially when under social or economic stress). Most live successfully in the community, either independently or in supervised settings.

For persons with moderate ID, the goals of education are to enhance adaptive abilities and “survival” academic and vocational skills so they are better able to live and function in the adult world (Table 53.7). The concept of supported employment has been very beneficial to these individuals; the person is trained by a coach to do a specific job in the setting where the person is to work, bypassing the need for a “sheltered workshop” experience and resulting in successful work adaptation in the community. These persons generally live at home or in a supervised setting in the community.

As adults, people with severe to profound ID usually require extensive to pervasive supports (Table 53.7). These individuals may have associated impairments, such as cerebral palsy, behavioral disorders, epilepsy, or sensory impairments, that further limit their adaptive functioning. They can perform simple tasks in supervised settings. Most people with this level of ID can live in the community with appropriate supports.

Abstract

Borderline intellectual functioning (BIF), that is to say, tested IQ levels in the range of 70–84/85, is prevalent, affecting about 12%–14% of the population depending on the exact level for “diagnostic” cutoff. In the current Diagnostic and Statistical Manual of Mental Disorders, BIF does not have a separate diagnostic category but can be categorized with a V-code. Children and adolescents with BIF usually struggle both as regards school performance and in respect of social functioning. BIF is common in attention deficit hyperactivity disorder, but sometimes attention problems in schoolchildren with BIF may be a consequence of nonadapted academic demands. Autism and BIF may also coexist, and there are many cases of so-called high-functioning autism who are high functioning only in the sense that they do not meet criteria for intellectual disability, but function in the area of BIF. Currently, too little attention is given to the negative effects of BIF on child development and adaptation. Learning, academic, and behavioral problems and grade retention may be markers of BIF. Our diagnostic and classification manuals need to have specific categories that clarify the problems that BIF entails so that affected individuals can avail themselves of better educational support and understanding.

Clinical Features

ID, also known as intellectual developmental disorder, requires limitations in both intellectual ability and deficits in adaptive skills, as expressed in conceptual, social, and practical adaptive skills, relative to the child’s age, experience, and environment. Specifically, the diagnosis requires that the following criteria are met: (1) Deficits in intellectual functioning (i.e., reasoning, abstract thinking, learning, both experiential and academic) that must be confirmed through both clinical evaluation and individualized, standardized IQ testing; (2) limitations in adaptive functioning that result in failure in meeting developmentaland social standards for personal independence and social responsibility; and (3) onset of intellectual and adaptive deficits occurs during the developmental period. Moreover, the level and severity of ID (mild, moderate, severe, and profound) is defined on the basis of adaptive skills rather than the IQ score. The definition links the severity of ID to the degree of community support required to achieve optimal independence (Katz and Lazcano-Ponce, 2008). Mild ID indicates the need for intermittent support; moderate ID for limited support; severe ID for extensive support; and profound ID for pervasive support. Although both intellectual and adaptive functioning are pertinent in defining ID, impairment of adaptive function is more likely to be the presenting feature than low IQ; however, it is expected that there is an association between intellectual functioning and adaptive skills.

The termglobal developmental delay (GDD) is used to describe children under the age of 5 years with significant delays in developmental milestones in several areas of functioning (APA, 2013b). GDD can be diagnosed using a standardized test, which shows performance at least 2 SD below the mean in at least two developmental domains: motor, speech and language, cognition, personal-social, and/or adaptive (daily living). The diagnosis of ID is not used for children under 5 years old since IQ scores are not reliable until after 5 years and because some children with a GDD diagnosis will not meet criteria for ID as they get older.

The IQ definition of ID uses 100 as the mean and 15 as the SD. An IQ score of 65–75 (≈2 SD below the mean, with a variation of ±5 points) is the demarcation point. Previously, children with an IQ of 55–69 were considered mild ID, those with an IQ of 40–54, as moderate ID; those with an IQ of 25–39, severe ID; and those with an IQ under 25, profound ID.

The prevalence of ID varies due to differences in diagnostic approach, population characteristics, and study design. In the general population, it is considered to be 1% when ID is defined as deficits in both adaptive and intellectual functioning (Harris, 2006; Maulik et al., 2011; Szymanski and King, 1999). The prevalence of intellectual deficits only (IQ < 75), based on IQ score alone, is 3% (Szymanski and King, 1999). Mild ID represents the majority (85%), but roughly 0.4% of the general population is severely intellectually disabled. As a rule, those with severe ID are more likely to have a definable biological cause, whereas those with mild ID tend to come from socially disadvantaged backgrounds and often have a family history of borderline intellectual function or mild ID (Kaufman et al., 2010; Stromme and Magnus, 2000). The prevalence of GDD (in children under 5 years) is estimated at 1%–3% (Shevell et al., 2003). The ratio of boys to girls with ID, especially mild ID, is 1.4:1. Male excess is present in ASD with ID, syndromic X-linked ID (S-XLID) (associated with a specific phenotype), and nonsyndromic X-linked ID (NS-XLID). About 15% of males with ID have X-linked intellectual disability (XLID) (Stevenson and Schwartz, 2009). About 25% of all males with severe ID have XLID, and almost 50% of all cases of mild ID are due to XLID (Partington et al., 2000; Ropers and Hamel, 2005). The recurrence of ID in families with one previous child with severe ID is reported to be between 3% and 9% (CDC, 2009).

Borderline Intellectual Functioning

Children in the Borderline Intellectual Functioning (BIF) group were included if they had prior FSIQ scores between 71 and 84 on a standardized measure of ability or met DSM-5 criteria for a diagnosis of borderline intellectual functioning. Data for the BIF group are shown in Table 10.4.

On the WISC-V, the borderline group obtained a mean FSIQ of 80.4, which was statistically significantly lower than the matched control group. The pattern of scores on the primary indexes was similar to those observed in the Mild and Moderate ID groups, although with higher means as expected. The highest score was obtained on the PSI, followed by the FRI, with lower scores across the other three domains. The ancillary index scores were similar to the primary index scores with mean scores in the 75–85 range. Unlike the Mild and Moderate ID groups, scores on the AWMI were not lower than scores on the WMI. In general, complementary subtest and index scores were similar to those observed on the primary and ancillary subtest and index scores. In addition, as noted earlier in the chapter and consistent with prior research, variability in group performance across subtests decreased as severity of disability moved from borderline to mild to moderate levels of intellectual functioning. The range of mean scores across subtests for the BIF group was 5.7–10.4, whereas it was 3.2–6.1 for Mild-ID and 2.0–4.6 for Moderate-ID.

Axis II

Axis II contains personality disorders (Table 17-2) and mental retardation (Table 17-3). Borderline intellectual functioning, although not considered a mental disorder, is also coded on Axis II. As with Axis I, multiple diagnoses should be listed on Axis II if present. If an Axis II diagnosis, rather than one or more co-morbid Axis I disorders, is the primary clinical concern, this may be noted by qualifying it in parentheses as principal diagnosis or reason for visit. Given that additional evaluation time or clinical information may be needed to diagnose Axis II disorders, it may be appropriate to specify no diagnosis or diagnosis deferred. In addition, personality traits that do not meet full criteria for a personality disorder, but are nonetheless maladaptive, may be listed on Axis II without the use of a diagnostic code, as may defensive patterns.4 The DSM-IV-TR provides examples of specific defensive patterns in Appendix B, in the “Glossary of Specific Defense Mechanisms and Coping Styles.” The Defensive Functioning Scale (pp. 807-810)5 is included as a “Proposed Axis for Further Study,” with the suggestion that this hierarchical ranking of defensive styles be placed below Axis V. In practice, inclusion of specific defensive patterns or a defensive level might be more easily incorporated into Axis II.4 Box 17-5 is an example of using Axis II in a way that may enhance clinical communication within a mental health care system.

Introduction

Intellectual disability, formerly called mental retardation (MR) is defined as having an IQ score below 70 whereas an IQ score in the range of 71–84 is termed as “borderline intellectual functioning”. Mental retardation is further subgrouped according to levels of IQ scores: mild MR (IQ: 50–70), moderate MR (IQ: 36–49), severe MR (IQ: 35–20), and profound MR (IQ < 20). The assessment of children younger than 5 years using a formal IQ test is not always possible. Also abnormalities at early ages may not exactly predict the future condition of MR; therefore the term “developmental delay” (DD) is preferred for young children (Schroeder et al., 2001).

The American Association on Mental Retardation (AMMR) defines MR as “a disability characterized by significant limitations both in intellectual functioning and in adaptive behavior as expressed in conceptual, social and practical adaptive skills” wherein the disability originates before 18 years of age (Luckasson et al., 2002). The definition by AAMR has three domains: intelligence, adaptive behavior, and systems of support; according to this definition IQ is not the only measure of MR. Mental retardation fundamentally affects the individual, the family, and society and is the third most common neurological condition following cerebral palsy and epilepsy in childhood. Mental retardation becomes evident in young children as developmental delay and eventually affects 1–10% of the population (McLaren and Bryson, 1987; Massey and McDermott, 1995; Stevenson, 1996). Mental retardation is more frequent in males with a sex ratio of 1.5:1 (American Psychiatric Association, 1995). The high prevalence of MR and DD exemplifies their impact on society and healthcare systems.

The diagnosis of MR is almost always straightforward yet determining the underlying etiology remains a challenge to every specialist involved in the care of the affected child. The extensiveness of the possible causes, the large number of laboratory investigations needed, and involvement of special services require that financial and professional resourses are available in the healthcare system. On the other hand, waiting for some time for a diagnosis to be established and having to face a lifelong medical condition–whether treatable or not–require the family to be patient and educated. Although most of the time the cause of MR is not treatable, establishment of a diagnosis enables the family to be aware of the short and long-term prognosis, risk for recurrences, and most importantly help them accept the disability.

Estimated likelihood of defining the etiology of mental retardation ranges between 10 and 81% (Curry et al., 1997; Shevell et al., 2003; Van Karnebeek et al., 2005a). In patients with severe mental retardation, establishment of an etiological diagnosis appears to be higher compared to mild cases. The factors accounting for such a wide range, other than the severity of mental retardation, could be the heterogeneity of the case series, the extensiveness of the laboratory investigations, and the complexity of the techniques, particulary the methods and tools used for genetic and neuroradiological studies.

There are extensive studies and reviews on the diagnostic evaluation of patients with MR/DD (Wilska and Kaski, 2001; Battaglia and Carey, 2003; Shevell et al., 2003; Van Karnebeek et al., 2005a, b). However evidence-based guidelines have not been established yet; available guidelines are mostly based on expert opinion. Table 21.1 summarizes the common clinical approach and diagnostic workup in a child with MR.

Table 21.1. Clinical approach and diagnostic work up in a child with mental retardation

Intellectual giftedness and disability

Figure 6.1 presents FSIQ and index score data from the WAIS-IV Technical Manual in graphical form for four groups with varying levels of intellectual functioning, ranging from intellectually gifted to moderately impaired. The gifted group (n = 34) had scores on a standard measure of cognitive ability that were at least 2 SDs above the mean, or had to have received special services from an intellectually gifted program in school. The intellectual disability groups (previously referred to as having varying degrees of mental retardation) had to meet DSM-IV-TR criteria that included subnormal scores on a standard cognitive ability measure in addition to showing evidence of impairment in adaptive functioning. The sample included 27 individuals with borderline intellectual functioning, 73 subjects with mild disability, and 31 with moderate disability.

The groups demonstrated clear separation of mean scores consistent with the diagnostic labels, with average FSIQ scores ranging from just below 50 in the moderate disability sample to over 125 in the gifted group. Among the index scores, the gifted group's lowest relative score was on PSI, with higher scores on VCI. Interestingly, PSI tended to be among the higher index scores across the borderline, mild, and moderate disability groups, although most index scores were similar. Subtest scaled scores for these groups are presented in Figure 6.2.

As seen in Figure 6.2, the intellectual disability groups show similar patterns of performance across most WAIS-IV subtests, with the lowest mean scores in the lower functioning groups on Letter–Number Sequencing, Digit Span, and Coding. The intellectually gifted group showed the highest scores on Vocabulary, Digit Span, and Information, with relatively lower scores (though, notably, still around the 75th percentile) on Symbol Search and Cancellation. The overall pattern of subtest scores furthermore shows the expected differences across groups, and all differed significantly from their respective control samples.

10.5.1.1 Intellectual ability

Intellectual ability, also sometimes referred to as general intelligence, is the acquired repertoire of general cognitive skills that is available to a person at a particular point in time [28] and can be measured via standardized scores on intelligence quotient (IQ) tests, also sometimes termed General Conceptual Ability (GCA) scores. The mean score for the neurotypical population is 100, and the standard deviation is 15. The International Statistical Classification of Diseases and Related Health Problems (ICD-10) suggests the following guidelines for classification of the degree of intellectual impairment: borderline intellectual functioning, IQ of 70–84; mild intellectual disability, IQ of 50–69; moderate intellectual disability, IQ of 35–49; and severe intellectual disability, IQ of 20–34. A systematic search of the literature indicated that almost all reported cases of Sotos syndrome have a degree of intellectual disability [24]. Tatton-Brown et al. (2005) [8] found that intellectual disability was present in 97% of 266 individuals with Sotos syndrome. However, in this study intellectual ability was determined via clinical assessment in which individuals were classified as having normal intellectual ability or mild, moderate or severe intellectual disability. This classification was based on clinical observation rather than via administration of standardized cognitive assessments.

Some of our work involved assessing intellectual ability using a standardized cognitive assessment in a cohort of 52 individuals with Sotos syndrome. The findings showed that the majority of the cohort had mild intellectual disability (IQ = 50–69) or were in the borderline range (IQ = 70–84). This evidence, therefore, supports the inclusion of intellectual disability as one of the main diagnostic criteria of the syndrome [26]. However, in this study, nearly 10% of the cohort tested had average intellectual ability (IQ = 85+). This highlights the variability of intellectual ability within this population and demonstrates that some individuals with Sotos syndrome do not have intellectual disability. Consequently, milder cases of Sotos syndrome may be harder to identify and diagnose if the clinical features are less severe.

Our study also analyzed whether there were any differences in intellectual ability in relation to gender. We found that females with Sotos syndrome had significantly higher GCA scores than males with Sotos syndrome. This suggests that, on average, males with Sotos syndrome may be more likely to have a greater degree of intellectual disability than females with Sotos syndrome. No significant relationship was identified between age and GCA scores, indicating that increase or decrease in intellectual ability is not associated with age within the Sotos syndrome population. However, as our study used a cross-sectional design, it will be important for future research to utilise a longitudinal design to establish the rate and trajectory of cognitive development within this population.

5.3 Sex

Hypothalamic Disorders Associated with Alterations in the HPA System

Many lesions of the hypothalamus, such as craniopharyngioma, Rathke’s pouch cysts, head trauma, inflammatory or infiltrative processes (meningitis, encephalitis, sarcoidosis, histiocytosis X) and brain tumors (including metastatic tumors and pinealomas) result in hypofunction of the HPA system secondary to destruction of the CRH-producing PVN neurons or to dissection of the pituitary stalk that transfers CRH from the hypothalamic median eminence to the pituitary gland.33–35 These pathologic conditions often result in impaired function of other hormonal axes, such as the hypothalamic–pituitary–gonadal or -thyroid axes, the growth hormone/insulin-like growth factor-I axis, and the water balance (antidiuretic hormone hyper- or hyposecretion).

Prader-Willi syndrome is a rare genetic disorder that is caused by deletion or non-expression of several genes (those for the small nuclear ribonucleoprotein polypeptide N, the nectidin, and a cluster of the small nucleolar (sno) RNAs) encoded on chromosome 15 (q11-13) (known as the PWS/AS region). It is characterized by a variety of symptoms associated with hypothalamic dysfunction, such as hypogonadism, hyperphagia, obesity, sleep disorders, learning disabilities/borderline intellectual functioning, and hypotonia.36,37 These patients (~60%) develop mild adrenal insufficiency, while overt adrenal insufficiency is relatively rare.38

A syndrome of paroxysmal periodic discharge, also known as Wolff syndrome, results in activation of the HPA system and subsequent elevation of circulating ACTH and cortisol concentrations.39 The following case was reported in 1964. The patient, a 14-year-old boy, demonstrated cyclic manifestations of nausea, vomiting, fever, emotional disturbances and marked weight loss.39 During the episode, he also showed elevated plasma ACTH concentrations and increased urinary excretion of glucocorticoid metabolites associated with hypertension, reduced glucose tolerance, and elevated serum cholesterol and free fatty acid concentrations. Activation of the HPA system appears to be secondary to the yet unknown underlying mechanisms of hypothalamic dysfunction. Similar cases, however, have not been reported thereafter.

Patients with major depression, particularly the melancholic type, demonstrate sustained hyperactivity of the HPA system and subsequent elevation of cerebrospinal fluid CRH, plasma ACTH and serum cortisol concentrations, possibly caused by mental stress.40,41 Activation of the HPA system in these patients occurs at the level of hypothalamus or higher brain centers. Patients with major depression have chronically elevated serum cortisol concentrations and therefore higher incidence of central obesity, hypertension, impaired glucose tolerance, decreased libido and osteoporosis.

Anorexia nervosa is also characterized by elevation of circulating cortisol concentrations through stimulation of the HPA system caused by strict energy restriction, as well as by mental stress.42,43 These patients demonstrate elevations of CRH in their cerebrospinal fluid,43 suggesting that the underlying activation of the HPA system is to some extent similar to that observed in major depression. In contrast to major depression, however, patients with anorexia nervosa do not show any clinical characteristics of glucocorticoid excess but rather present with those associated with reduced action of glucocorticoids, such as hypotension, hypoglycemia and decreased lipid concentrations. Thus, the biologic actions of circulating glucocorticoids are not manifested in the glucocorticoid target tissues of these patients possibly because of the lack of food substrate and changes of proteins that may influence the actions of glucocortcoids, such as the AMP-activated protein kinase and the forkhead transcription factors.44,45

The conditions associated with uncoupling of the circadian rhythm between the CNS and peripheral tissues, caused, for example, by frequent trans-time-zone travel and night-shift work, are likely to result in increased action of glucocorticoids in local glucocorticoid target tissues, which predisposes subjects to cardiovascular morbidity and mortality.4 It was recently reported that the Clock transcription factor, an essential component for generating circadian rhythm in the CNS (central CLOCK) and peripheral tissues (peripheral CLOCK), regulates GR transcriptional activity, and this effect of CLOCK on GR may cause “functional” glucocorticoid hypersensitivity through uncoupling of circulating cortisol concentrations and peripheral target-tissue sensitivity to glucocorticoids.4,46