**5. Differentiation: Why and how?**

#### **5.1. Overlap and differences**

The overlap in symptoms between autistic and non-autistic people with sensory and intel‐ lectual disabilities must be clear after reading this chapter. The diagnoses of ASD is usually based on behavioural characteristics and these can be similar in autistic and non-autistic people with additional impairments. An additional problem is that, although instruments are available for people with intellectual disabilities [63, 64], most of the current test instru‐ ments do not have separate norms for people with sensory and/or intellectual disabilities. No valid instruments are available for deaf people according to Jure and colleagues [14], nor for visually impaired people [7]. The overlap in symptoms and trouble in diagnosis cause a distorted representation of ASD in people with sensory, intellectual and multiple impair‐ ments. Some people are diagnosed as autistic when they are not, while others do not get the autistic label when they should. So there is both an overdiagnosis [5, 15] of ASD in this group, meaning that more people are diagnosed as autistic than necessary because of these overlapping symptoms, as well as an underdiagnosis [14, 65]. In a group of deaf children, for example, the diagnosis of ASD was established significantly later than in a group of hearing children. Autistic behaviours were probably missed because of an earlier diagnosis of hearing impairments or other developmental disabilities [65]. The main problem in as‐ sessment of ASD can be attributed to a diagnostic overshadowing bias. The diagnostic over‐ shadowing bias was first described for people with intellectual disabilities and is the tendency of clinicians to overlook symptoms of mental health problems in this group and attribute them to being part of "having an intellectual disability" [66]. In the presence of mental retardation it seems that the diagnostic importance of abnormal behaviour decreases. Blindness, deafness or deafblindness all might add an extra overshadowing bias next to in‐ tellectual disability, leading to either false positive or false negative diagnoses of ASD in people with these disabilities.

Despite the obvious similarities between autistic and non-autistic people with sensory and intellectual disabilities, this chapter also outlines that even though the symptoms ap‐ pear the same, sometimes subtle difference can still be found. This may be due to the possibility that underlying processes of the behaviours are different for autistic and nonautistic individuals [4, 5, 15]. If attempted, a differentiation can thus be made by study‐ ing the subtle differences and underlying causes. A couple of years ago, this was done by making a valid instrument to diagnose ASD in people one of the most challenging combination of disabilities, namely deafblindness and profound intellectual disabilities. Hoevenaars-van den Boom and colleagues were able to confirm the huge overlap in be‐ havioural symptoms between autistic and non-autistic people, but were also able to suc‐ cessfully distinguish the autistic from non-autistic people with their approach that was suited to the developmental level of the participants. They found that differences in this group can be found in the social communicative field, mostly in openness for contact, reciprocity and joint attention and communicative functions [7]. It is clear that when us‐ ing a careful and sophisticated approach, a distinction can be made between autistic and non-autistic people with sensory and intellectual disabilities

#### **5.2. Interaction, treatment and teaching**

Whereas stereotyped movements in people without ASD are part of a normal develop‐ ment, in people with ASD they are part of their syndrome. Gense and Gense [20] believe that the differences between these behaviours in visually impaired people with or with‐ out ASD can be found in the severity and perseverance of this behaviour. People with ASD show higher intensities and stronger persistence in stereotypical behaviours [20, 57]. Similar to the behaviours in the intellectually disabled, this could be due to a lack of ex‐ ternal stimulation. Especially in the blind, where stimulation from visual input is miss‐ ing, self-stimulatory stereotyped movements could provide the necessary sensory stimulation [18]. Another difference between people with ASD and people without, is that stereotyped behaviour can more easily be interrupted or stopped in people with vis‐ ual impairments alone [20]. Sometimes not much more has to be undertaken than mak‐ ing the blind person conscious of these unconsciously executed stereotyped behaviour

The overlap in symptoms between autistic and non-autistic people with sensory and intel‐ lectual disabilities must be clear after reading this chapter. The diagnoses of ASD is usually based on behavioural characteristics and these can be similar in autistic and non-autistic people with additional impairments. An additional problem is that, although instruments are available for people with intellectual disabilities [63, 64], most of the current test instru‐ ments do not have separate norms for people with sensory and/or intellectual disabilities. No valid instruments are available for deaf people according to Jure and colleagues [14], nor for visually impaired people [7]. The overlap in symptoms and trouble in diagnosis cause a distorted representation of ASD in people with sensory, intellectual and multiple impair‐ ments. Some people are diagnosed as autistic when they are not, while others do not get the autistic label when they should. So there is both an overdiagnosis [5, 15] of ASD in this group, meaning that more people are diagnosed as autistic than necessary because of these overlapping symptoms, as well as an underdiagnosis [14, 65]. In a group of deaf children, for example, the diagnosis of ASD was established significantly later than in a group of hearing children. Autistic behaviours were probably missed because of an earlier diagnosis of hearing impairments or other developmental disabilities [65]. The main problem in as‐ sessment of ASD can be attributed to a diagnostic overshadowing bias. The diagnostic over‐ shadowing bias was first described for people with intellectual disabilities and is the tendency of clinicians to overlook symptoms of mental health problems in this group and attribute them to being part of "having an intellectual disability" [66]. In the presence of mental retardation it seems that the diagnostic importance of abnormal behaviour decreases. Blindness, deafness or deafblindness all might add an extra overshadowing bias next to in‐ tellectual disability, leading to either false positive or false negative diagnoses of ASD in

patterns.

**5. Differentiation: Why and how?**

492 Recent Advances in Autism Spectrum Disorders - Volume I

**5.1. Overlap and differences**

people with these disabilities.

A fair diagnosis of ASD, or no ASD, is very important for the treatment and interaction with people with sensory and intellectual disabilities. An ASD diagnosis or a lack thereof will af‐ fect how a person will be treated, as autistic or not. If a child with ASD is placed in a setting where his or her ASD goes unrecognized, the clinicians and care takers might fail to respond to the needs of this person [65]. An important example of why recognition of ASD is so im‐ portant is the treatment of stereotyped behaviour. Stereotyped movements can be a way to reduce stress [19, 20]. In someone with no ASD but with blindness or deafblindness, this be‐ haviour is usually caused when the person does not get enough stimulation from their envi‐ ronment [17, 18], whereas in persons with ASD stereotyped behaviours can be a way to escape from overstimulation or as a way to ensure the optimal level of arousal. In both cases the way to treat stereotyped behaviour will be different, give extra stimulation or reduce overstimulation, respectively. A valid diagnosis would be very helpful in cases where clini‐ cians or parents have to decide what kind of intervention to give. If it is clear whether some‐ one has ASD or not treatment and interaction can be adjusted. Someone with ASD needs a more structured environment, and needs clear instructions when something needs to be done. In someone with ASD, things need to be re-explained in new situations, because of their difficulties in generalizing [6]. It also seems that the sooner we are aware of ASD the better. People with ASD need to be approached in way that is accommodated to their needs [65], and for the wellbeing of the child, it is best if this is done as soon as possible. A recent meta-analysis on intensive early intervention programs for ASD shows that programs that intervene early are most effective and can produce changes in the area of language and adaptive behaviour [67]. Adaptive behaviour was also found to increase as well when addi‐ tional behavioural treatments were given to children with ASD and intellectual disabilities [68]. These studies showed that if ASD is treated, successful results can be achieved.

As can be seen throughout this chapter, people with visual impairments show many behav‐ iours that are similar to ASD, such as the lack of understanding of social situations, ego-cen‐ teredness, and lack of understanding gestures and facial expressions. But, according to Gense and Gense [20], these behaviours may still be taught. Teaching appropriate behav‐ iours is especially important, because inappropriate behaviours may interfere with regular social interactions [18], depriving disabled children of these otherwise valuable experiences. And whereas for non-autistic people without visual impairments these behaviours are im‐ plicitly learned, in non-autistic visually impaired people, they need to be explicitly taught. With the right type of education, visually impaired people may still learn to interpret social situations, read and understand gestures and facial expressions and learn to play with oth‐ ers [20]. This was also found for two severely mentally disabled deafblind young men, of whom the social interaction became significantly better after tailored training sessions [58]. Although this was only a small study with two participants, it does indicate what a special‐ ized training can mean for children that are not restrained by ASD. The same applies to lan‐ guage. When a delay in language is caused by a lack of seeing things to talk about, parents need to offer more tactile or auditory stimuli [18]. Basically, it is important to take into ac‐ count everything that singular or multiple disabled people lack. When sensory and intellec‐ tual impairments are involved, one needs to try and substitute the missing modality for others as much as possible.

impaired people. Ideally, a new way to assess autistic behaviours in sensory and intellectually disabled people that takes into account all the difficulties that assessing this group brings forth will be developed. An instrument that can make accurate diagnosis in people with multiple disabilities should account for all the overlapping symptoms and differences that have been described. First of all, intellectual disabilities should be taken into account. Some behaviours that are typical for ASD in people without intellectual disabilities can be simply explained by a person's mental age or shortcomings in intellectual abilities. An example of this is theory of mind, and related to that joint attention, symbolic play and language abilities, that do not de‐ velop until a certain age. If an intellectually disabled person has not reached a sufficient mental age, these behaviours should not be used to assess ASD. Secondly, it's important to realise that sensory disabilities withhold a person from perceiving objects and situations the same way a person without sensory disabilities would and may follow a completely different path. When someone is visually impaired or blind, eye contact, following gaze and sharing attention through pointing cannot be used as differentiating characteristics. Furthermore, it's important to take into account that a person may not always be aware of the presence of objects or people, so failures to respond like a person without ASD can be caused by being unaware of their pres‐ ence in the first place. Similar precautions should be made for deaf people, who are unable to respond to calling their names, other sounds, and may not even notice the arrival or departure of a person. Finally, a combination of these disabilities can make it more challenging to make diagnostic evaluations of a person. People with multiple disabilities may need more time to process their surroundings and to realise what is expected of them. Furthermore, unexpected and sudden movements or actions, or giving too much information at once may cause a lot of stress that interferes with their performance. Many characteristics that normally differentiate people with ASD from people without ASD should not be assessed or assessed differently in people with multiple impairments. Still, some characteristics of the autistic spectrum are left that can be included in an assessment. Examples that cannot be forgotten include interest in, re‐ sponse to and looking for contact, resistance to change and interest in new items or situations. Sharing of feelings or interests may not occur through pointing or gaze, but may show itself in a more tactile way. It is important to be aware of the different way in which multiply disabled people express themselves. Finally, to account for intellectual disabilities, it is important to as‐ sess everything on a level that is suitable for the participants. Do not use complicated question‐ naires, but simple toys as much as possible. Only if all of this can be done successfully, autistic

Autism Spectrum Disorders in People with Sensory and Intellectual Disabilities – Symptom Overlap and Differentiating

Characteristics

495

http://dx.doi.org/10.5772/53714

people can be differentiated from non-autistic people and personal needs can be met.

1 Behavioural Science Institute, Radboud University Nijmegen, NijmegenThe Netherlands,

, Harry Knoors1,2 and Ludo Verhoeven1

**Author details**

Gitta De Vaan1\*, Mathijs P.J. Vervloed1

\*Address all correspondence to: g.devaan@pwo.ru.nl

2 Royal Kentalis, Sint-Michielsgestel, The Netherlands

### **6. Summary and Conclusion**

Many characteristics of ASD seem to overlap with characteristics that are naturally present in people with sensory disabilities, intellectual impairments or a combination of disabilities. The characteristics appear the same whether ASD is present or not, which makes it difficult to make a valid diagnosis of ASD in this group. All of the criteria that are used in DSM-IV-TR to define ASD are, to some extent, also present in people with one or more of these disa‐ bilities. However, if one would look closer to these criteria, and the way they are expressed within people with sensory and intellectual impairments, slight and subtle differences can be found. There are differences in the way the symptoms express themselves, the severity of the symptoms and the underlying causes for the behaviours. Problems also occur in meth‐ odology. Paradigms that are used to assess problems that are related to ASD, such as ToM tasks, fail to be successful in differentiating people with sensory or multiple impairments. This overlap and these problems in methodology make it a major challenge to diagnose ASD within people with sensory and intellectual disabilities.

The slight differences in the way symptoms are expressed show that a distinction between au‐ tistic behaviours and non-autistic behaviours can be made. Making this distinction is very im‐ portant to do, because the needs of people with ASD differ very much from people without ASD. To make sure the needs of every individual are met, people should be diagnosed in the right way. This is especially important for those groups with problems in communicating their wants and needs. In order to do this, subtle differences need to be taken into account. Up until this day, no instrument is suited to diagnose ASD or assess autistic behaviours within multiply impaired people. Ideally, a new way to assess autistic behaviours in sensory and intellectually disabled people that takes into account all the difficulties that assessing this group brings forth will be developed. An instrument that can make accurate diagnosis in people with multiple disabilities should account for all the overlapping symptoms and differences that have been described. First of all, intellectual disabilities should be taken into account. Some behaviours that are typical for ASD in people without intellectual disabilities can be simply explained by a person's mental age or shortcomings in intellectual abilities. An example of this is theory of mind, and related to that joint attention, symbolic play and language abilities, that do not de‐ velop until a certain age. If an intellectually disabled person has not reached a sufficient mental age, these behaviours should not be used to assess ASD. Secondly, it's important to realise that sensory disabilities withhold a person from perceiving objects and situations the same way a person without sensory disabilities would and may follow a completely different path. When someone is visually impaired or blind, eye contact, following gaze and sharing attention through pointing cannot be used as differentiating characteristics. Furthermore, it's important to take into account that a person may not always be aware of the presence of objects or people, so failures to respond like a person without ASD can be caused by being unaware of their pres‐ ence in the first place. Similar precautions should be made for deaf people, who are unable to respond to calling their names, other sounds, and may not even notice the arrival or departure of a person. Finally, a combination of these disabilities can make it more challenging to make diagnostic evaluations of a person. People with multiple disabilities may need more time to process their surroundings and to realise what is expected of them. Furthermore, unexpected and sudden movements or actions, or giving too much information at once may cause a lot of stress that interferes with their performance. Many characteristics that normally differentiate people with ASD from people without ASD should not be assessed or assessed differently in people with multiple impairments. Still, some characteristics of the autistic spectrum are left that can be included in an assessment. Examples that cannot be forgotten include interest in, re‐ sponse to and looking for contact, resistance to change and interest in new items or situations. Sharing of feelings or interests may not occur through pointing or gaze, but may show itself in a more tactile way. It is important to be aware of the different way in which multiply disabled people express themselves. Finally, to account for intellectual disabilities, it is important to as‐ sess everything on a level that is suitable for the participants. Do not use complicated question‐ naires, but simple toys as much as possible. Only if all of this can be done successfully, autistic people can be differentiated from non-autistic people and personal needs can be met.
