Introduction

Emotional and behavioral problems are a significant extra dimension that burdens the lives of many children with intellectual disabilities (ID) and their families and carers. This psychopathology is a major barrier to community and educational participation and inclusion and is associated with high levels of family stress, parental mental health problems, and reduced family quality of life (Tonge and Einfeld, 2003; Gardiner and Iarocci, 2012). Young people with ID have about three to four times as much psychiatric disturbance as children of average intelligence. Rutter et al. (1970), in their Isle-of-Wight population study, found that 50% of children with ID with an IQ below 70 had a psychiatric disorder, compared with 6.8% of children with an IQ above 70. Corbett (1979), in a study of the urban area of South-East London, found a prevalence rate of psychiatric disorder of 47% in children aged up to 15 years with an IQ below 50.

A longitudinal epidemiological study of intellectually disabled Australian children aged between 4 and 18 years found that 41% had a clinically significant emotional or behavioral disorder (Einfeld and Tonge, 1996). The study also found that disruptive and antisocial behaviors were more common in young people with ID, and that self-absorbed and social-relating problem behaviors were more common in young people with more severe ID. In contrast to general childhood psychopathology, age and sex did not affect prevalence, probably due to the salience of neurobiological influences, particularly for those with more severe ID. Over time into adult life, levels of psychopathology, although remaining substantial, decreased more in males than females and more for young people with mild ID (Einfeld et al., 2006). Of concern was that fewer than 10% of these children with ID had received any specialist mental health services.

An epidemiological study of a national survey of mental health information on more than 10 000 children aged 5–15 years in Great Britain revealed that 39% of children with ID met DSM-IV and ICD-10 criteria for at least one psychiatric disorder, compared to 8.1% of children without ID (Emerson, 2003). Emerson et al. (2009) demonstrated an association between psychopathology in children with ID and family socioeconomic hardship and disadvantage, but this association might not apply to families of children with ID and autism (Gray et al. 2012).

Phenomenology

Children with ID can suffer from the full range of psychopathological disorders experienced by children of normal intelligence. Although the diagnosis of psychiatric disorders is unlikely in preschool children, there is evidence that by age three, developmentally delayed children are three times more likely to have a clinically significant level of emotional and behavioral disturbance that persists to age four (Baker et al. 2002, 2003). Anxiety disorders, depression and bipolar affective disorders, attention-deficit/hyperactivity disorder (ADHD), schizophrenia, and psychotic disorders have all been described in young people with ID (Matson and Barrett, 1982). Children with ID, compared to children without ID, are at greater risk for ADHD, conduct disorders, depression, anxiety disorders (including separation anxiety and phobias), and autistic disorder (Stromme and Diseth, 2000; Emerson, 2003; Tonge and Einfeld, 2003). ID is present in at least 70% of cases of autism (Volkmar and Klin, 2005). The types of psychopathological disorders in children with mild ID are more likely to resemble those found in the general population. It is increasingly difficult for the clinician to apply the criteria of existing diagnostic classifications in young people with more severe levels of ID who do not have the ability to share with others the content of their thinking and emotional experience. In these circumstances, a diagnosis must be made on the basis of observed behaviors and change in patterns of behavior, daily living skills, interests, social interaction, and interpersonal relationships.

There are some patterns of disturbed emotions and behaviors in young people with ID that cannot be adequately described by current psychiatric diagnostic systems such as the ICD-10 (World Health Organization, 1992) and the DSM-5 (American Psychiatric Association, 2013). The validity of these two major systems of psychiatric diagnosis is yet to be demonstrated when applied to young people with ID.

Another approach to the description of emotional and behavioral problems is the quantitative taxonometric model based on the statistical analysis of symptom questionnaires collected on defined populations of individuals with ID (Aman, 1991). An example of this approach in children are studies using the Developmental Behavior Checklist (DBC), a reliable and valid 96-item questionnaire of emotional and behavioral problems in young people with ID that is completed by parents, or carers, or teachers (Einfeld and Tonge, 2002). Since 1990, these studies have followed the mental health of a representative sample of 578 Australian young people with ID who were initially aged between 4 and 18 years (Tonge et al., 1996; Tonge and Einfeld, 2003; Einfeld et al., 2006). At the beginning of this study, 45% of the children had clinically significant levels of emotional and behavioral disorder. Symptoms of ADHD manifest as poor concentration, distractibility, impulsiveness, and hyperactivity, and were present in 32% of the children. The symptoms were not related to gender, in contrast to the general population where ADHD is more prevalent in males. The prevalence of ADHD symptoms was significantly reduced to 14% over 14 years as the young people moved into late adolescence and early adult life, suggesting a maturational effect. This happened at a faster rate for girls (decreasing to 9%) than for boys (decreasing to 17%). A total of 9% of the children were reported by their parents to have persistent symptoms of depression, tearfulness, irritability, and low self-esteem. This prevalence of depression did not change over 14 years and was not related to gender, in contrast to the general population where depression increases through adolescence and is more common in females. These symptoms of depression were less prevalent (3%) among those with severe or profound ID.

Initially, 8% of the children suffered from anxiety and phobias and there was no significant gender difference. Over the next 14 years, the prevalence of anxiety disorders did not change among boys, but increased among girls to 20%. In the general population of young people, females are twice as likely as males to suffer from anxiety disorders (Tonge, 1988). Those with severe or profound ID had a lower prevalence of anxiety disorders. These findings indicate that psychopathological disorders of childhood such as ADHD, depression, and anxiety were at least 4–5 times more prevalent in children with ID than in other children. Comorbidity was also common, with 19% of the children with ADHD also suffering from depression and 12% from anxiety. For children with depression, 70% also had ADHD and 30% had anxiety. This burden of specific psychopathological disorders in young people with ID (Tonge and Einfeld, 2003) highlights the imperative for better assessment and treatment services for this at-risk group of children.

Clinical assessment

The clinical interview is the essential component in diagnosis and assessment and is, therefore, necessary in the process of deciding on a rational management and treatment plan. The presence and severity of ID in the child necessitates some modification of a routine child psychiatric assessment and mental state examination. Information from the parents or carers and teachers and direct observation of the child, preferably in a variety of settings, such as at school as well as at the clinician’s office, are essential. There is usually a range of contextual problems and factors that influence and complicate the presentation of emotional and behavioral problems in young people with ID, which need to be taken into account in order to achieve a satisfactory assessment diagnosis and a rational treatment plan (Tonge and Einfeld, 1991).

Cox and Rutter (1985) have demonstrated that the combined use of non-directive interview techniques together with more directive and structured questions, supplemented by parent- and teacher-completed checklists, provides the most comprehensive information and significantly improves assessment and diagnosis. This combined, unstructured and structured approach is still effective in promoting rapport and the expression of affect.

This approach to assessment and diagnosis has been replicated in an analysis of 70 psychiatric assessments of children with ID (Einfeld and Tonge, 1993). The non-directive interview component of the assessment revealed parental concern regarding an average of nine symptoms; compared to an average of 35 symptoms scored by the parents on a DBC they had previously completed (Einfeld and Tonge, 1993). The use of a parent- or carer-completed checklist, such as the DBC, clearly enriches the clinical assessment process, and parents reported that they felt the problems they faced had been fully explored and understood.

It is useful during part of the assessment to interview the parents or carers and the child together, and if the child can manage the separation, it is essential to see the child individually. Information from others, such as teachers, provides a broader perspective as well as information on contextual elements of the child’s emotional or behavioral problems, and more resilient and adaptive behavior. A comprehensive cognitive assessment is also necessary in order to place the child’s behavior into a developmental perspective and to understand the influence and impact of any cognitive impairments or specific pattern of cognitive performance on behavior, communication, and comprehension. For example, children with autism usually have better visual and performance skills than verbal and social comprehension skills, which can account for some of their frustration and difficult behavior, and has implications for education and management. Developmentally excessive problems with inattention during the cognitive testing may point to ADHD or anxiety, and deficits detected in working memory might account for disruptive and oppositional behavior in the classroom.

Assessments of communication and motor skills can also add considerable information to the overall picture. To date, there are no standardized general psychiatric assessment interviews validated for use with young people with ID. The parent’s version of the Anxiety Disorders Interview Schedule (Albano and Silverman, 1996), which provides an algorithm for DSM-IV diagnoses, is being used in some clinical studies of anxiety disorders in children with moderate or less severe levels of ID. In the specific area of autism spectrum disorders, Lord et al. (1994) have developed the Autism Diagnostic Instrument (ADI), which comprises a structured parental interview. The ADI is supplemented by a clinician-led, structured play–task interaction with the child; the Autism Diagnostic Observation Schedule (ADOS) (Lord et al. 1999; Gray, et al. 2008). The ADI/ADOS provides a reliable and valid diagnosis of pervasive developmental disorders (Hus and Lord, 2014). It requires a skilled clinician to administer and is appropriately time-consuming, given the complexity and the serious implications of this diagnosis.

It is evident that the psychiatric assessment of young people with ID is complex, and requires information from all those involved in their care, as well as detailed mental state, psychological, developmental, and physical assessment of the child, together with any special investigations that may be indicated, such as genetic or imaging studies. This process is usually of necessity a multidisciplinary one, requiring contributions from psychiatrists, psychologists, pediatricians, and, when appropriate, others such as speech pathologists, occupational therapists, physiotherapists, and special teachers. To be effective, this multidisciplinary assessment requires coordination, usually through a case conference in which one of the specialist clinicians is designated as the case manager.

Developmental level and cognitive ability

The diagnosis of many psychiatric disorders requires an assessment of the person’s thought processes and content. This may be possible in a child with mild ID and some communication skills, but becomes progressively more difficult as the level of ID becomes more severe (Forster et al., 2011). The clinician must often rely on observation of behavior and signs such as adverse changes in play interests, social participation, appetite, sleep, and activity level, as well as observed mood, to make a presumptive diagnosis of mental disorder (Costello, 1982; Sovner, 1986).

The developmental level of a child must also be taken into account when assessing the significance of problem behaviors. Normal behaviors in young children, such as separation anxiety or short attention span, may be seen in a much older child with ID who is still functioning at that younger developmental level. This necessity to take a developmental perspective is required by some diagnoses. For example, the DSM-5 (American Psychiatric Association, 2013) and the ICD-10 (World Health Organization, 1992) require that to make a diagnosis of attention-deficit/hyperactivity disorder (hyperkinetic disorder), the behavioral symptoms must be developmentally excessive for a child of the same mental age and developmental level. The assessment of antisocial, aggressive, and defiant behavior should take into account the child’s developmental level and capacity to understand social rules and right from wrong when making a diagnosis of conduct disorder. A consideration of this capacity usually excludes children with autism or more severe levels of ID from the diagnosis of conduct disorder. In some children, organic deterioration of cognitive ability, the effects of some medications on the brain, the consequences of fetal alcohol or other substance spectrum disorder on the function of the frontal lobe, or the behavioral consequences of puberty and hormonal changes may also cause psychopathological symptoms and complicate or alter response to treatment.

Multiple disabilities and medical illness

Children in the general population with chronic illness that affects the brain have a higher prevalence of associated psychiatric disorder (Tonge, 1991). Children and adolescents with ID are more likely than the general population to have a range of physical and sensory impairments and medical illness, which further increases the risk of emotional and behavioral problems (Sovner and Hurley, 1989). For example, deafness may lead to behavior that is seen in autistic children or children with conduct disorder. Hearing impairment may also aggravate psychiatric disorders such as separation anxiety. Children with ID, particularly those with more severe ID, are much more likely to have medical illnesses or abnormalities of the brain, such as epilepsy, where the risk is even higher (Amiet et al., 2008). Epilepsy can cause disturbed behavior and aggravate existing emotional and behavioral problems, particularly if the epilepsy is poorly controlled (Lewis et al., 2000). The onset of depression and a loss of interest in usual activities during adolescence might herald this decline (Einfeld and Tonge, 2000). Autism is associated with a range of medical conditions, such as tuberous sclerosis, and other psychiatric conditions, such as Tourette syndrome (Volkmar and Klin, 2005). Specific patterns of behavior are also evident as the behavioral phenotypic expression of some genetic disorders (see also Chapter 18). Intellectually disabled children may also not be able to communicate effectively that they are suffering from pain or the symptoms of a fever or physical illness. Instead, they may exhibit disturbed behavior such as irritability, restlessness, or withdrawal, which may be misunderstood as being due to a psychiatric disorder.

Psychosocial and family factors

Children and adolescents with ID are more likely than the general population to experience a range of psychosocial stresses and environmental experiences that adversely affect their personality development, emotional adjustment, and attachment behavior, and can result in impoverished or distorted and inappropriate social behavior (Sovner, 1986; Aman and Schroeder, 1990). The families of children living in alternative residential or foster care may not be available for interview to provide reliable developmental and family histories. Institutional records often give an unreliable and inadequate account of the person’s history. Observation and assessment of the child’s interaction with their family, or with foster parents or staff and residents of an alternative care environment, are essential in order to understand the behavior in its psychosocial context and the contribution that these interactions make to the psychopathology. For example, in response to environmental stress, some children with ID may experience a regression and disintegration of their already impaired cognition, resulting in bizarre and psychotic-like behavior that can be misdiagnosed as schizophrenia. Another child might be withdrawn, listless, and apathetic in response to parental overprotection and lack of stimulation. Environmental deprivation and abuse, and a lack of stimulation and opportunity for play, activity, and socialization, aggravate ID, prevent children from reaching their full potential, and lead to a range of attachment, personality, emotional, and behavioral problems, and handicaps.

Although some parents have a positive and life-enriching experience caring for a child with ID, for many there is an increased risk that they may suffer from mental health problems and stress, particularly when the child also has emotional and behavioral problems (Baker et al., 2003; Blacher et al., 2007; Lloyd and Hastings, 2008). Therefore, the effective management of emotional and behavioral disorder in a child with ID may also require parent education and skills training and support, and management of any parent mental health problems, such as maternal depression or paternal alcohol abuse.

Management principles

Successful management begins with the establishment of a positive relationship with the parents and carers, and, if possible, the child during the assessment process. A working diagnosis that takes into account the biological, psychological, and social contributing factors, and context provides the key to a rational management plan. Treatment is usually multimodal, requiring a combination of parent support and skills training, behavioral interventions, modifications to the social and educational environment, modified psychological treatments, and, as a second line of treatment in combination with psychological and supported management, the use of psychoactive medication when indicated.

Some young people with moderate or less severe levels of ID have sufficient communication skills and understanding of consequences to be able to benefit from a modified form of cognitive-behavioral therapy. This involves a combination of relaxation training, modeling and reinforcement of confident and pro-social behaviors, formulating positive self-thoughts and statements instead of negative attributions, and providing a structured experience of rewarding educational and social activities and skills.

There is no evidence that family therapy has a direct effect, but it does reduce family dysfunction and conflict, and modifies problematic family interactional patterns, such as parental overprotection, which contribute to psychopathology in the child. The provision to the parents of educational information on ID in general, and on the nature of the ID and the psychopathological disorder in their child in particular, helps the parents generate their own adaptive responses and cooperate as partners with a range of services in the management of their child. A cooperative working relationship with the parents makes it more likely that they will feel encouraged to share their grief regarding their child’s disability, and this in itself is also therapeutic. Structured parent education and skills training to manage problems such as disruptive behavior, anxiety, and communication difficulties in children with ID leads to sustained improvements in parental mental health, child behavior, and family life (Roux et al. 2013; Tonge et al. 2014). Counseling and the provision of psychological and educational interventions for siblings may also be necessary to promote family functioning.

Behavior management using operant conditioning techniques can be an effective strategy for managing difficult behaviors. The design of an effective behavior-modification program requires a detailed behavioral analysis regarding the context, the communication intent of the behavior, consequences that reinforce the behavior, the response by others to the behavior, and the longer term consequences of the behavior.

There is a secondary role of medication, but it should form part of a broader psychotherapeutic and supportive management plan. Most research on the use of pharmacotherapy in children with ID is focused on aggression and self-injurious behaviors. Controlled trials of haloperidol and, more recently, risperidone have shown that they are effective in the treatment of aggression, hyperactivity, and stereotypic behaviors, particularly in intellectually disabled children with autism, although these medications are associated with extra-pyramidal symptoms and other adverse side effects, such as weight gain and its metabolic consequences, and cardiac dysfunction with prolongation of the electrocardiograph QTc interval (Campbell et al., 1993; Lindsay and Aman, 2003). Lithium, carbamazepine, beta-blockers, such as propranolol, and the alpha-2 antagonist clonidine have been shown (mostly in open trials) to reduce aggressive, disruptive, and agitated behavior. Opiate agonists and antagonists (e.g., naloxone and naltrexone) may have some role in reducing self-injurious behaviors (Botteron and Geller, 1993). Stimulant medications such as dexamphetamine and methylphenidate may be useful in the treatment of unequivocal ADHD (Birmaher et al., 1988; Dulcan, 1990), but the efficacy of the more recent atomoxetine in children with ID has not yet been established. A favorable response to stimulant medication in developmentally disabled children and those with autism who also have ADHD may not be as marked as in children with ADHD who do not have ID. In young people with more severe ID, stimulant drugs may even exacerbate stereotypic and disturbed behavior. Anxious and obsessional behavior in intellectually disabled young people, particularly those with autism, may respond to treatment with selective serotonin reuptake inhibitors (SSRIs), such as fluoxetine, and the older tricyclic antidepressants, such as clomipramine and imipramine, but firm evidence from controlled trials is still required, and it is not clear if these reported therapeutic effects are due to specific effects on serotonin metabolism. Medication treatment requires regular follow-up and monitoring for compliance, the development of side effects, and therapeutic response. It is preferable to document the therapeutic response through the repeated use of behavioral observations and a symptom checklist.