An Introduction to Autism
Developmental disorders are described as a group of conditions with an onset in infancy or childhood. They are characterised by a varying degree of impairment or delay in functions. These are related to the development of the central nervous system. They usually improve with age but in some instances may lead to impairments or difficulties which continue throughout adult life. Depending upon the area of development affected, the disorder could be specific to one single area (e.g. specific developmental disorders of speech and language, of scholastic skills, or motor function) or several areas (e.g. pervasive developmental disorders, Autistic spectrum disorders and intellectual disability). This short article will discuss the Autistic spectrum disorder and its subtypes.
Pervasive Developmental Disorder (PDD) or Autism spectrum disorder (ASD)
These two terms have been used interchangeably in the literature as a subtype of developmental disorder. The term Pervasive Developmental Disorder (PDD) was coined by the American Psychiatric Association and is most widely used in American studies and literature. In contrast, the term Autism Spectrum Disorder (ASD) is more commonly used in Europe. There are some minor differences in their use such as Pervasive Developmental Disorder (PDD) covers Autism and related conditions such as Rett’s syndrome or Fragile X syndrome. ASD covers conditions which clearly fall on the Autism spectrum such as Autism and Asperger syndrome, although on occasions these boundaries are blurred in literature. It is argued that PDD excludes the negative connotations of ASD but at the same time it signifies conditions are pervasive of all aspects of development. In the International Classification of Diseases (ICD -10) the term used is Pervasive Developmental Disorder (ICD-10 F84).
According to the International Classification of Diseases and Related Health Problems – 10th Edition, ASD is the term frequently used to refer to the group of disorders which are “a group of disorders characterised by qualitative abnormalities in reciprocal social interactions and in patterns of communication, and by a restricted, stereotyped, repetitive repertoire of interests and activities“. In simpler terms, disorders with symptoms and behaviours which affect the way in which a group of people understand and react to the world around them. As the name suggests it is a spectrum which includes different forms of Autism and syndrome. Many children may share similar difficulties, the way that these affect them can vary in presentations.
Overall incidences reported by the Centre of Disease Control and Prevention of ASD is 1 in 68. In the UK, it’s estimated to be 1% which translates to about one in every 100 people. It is estimated to be more prevalent in boys than in girls, with the disorder usually presenting itself before the age of Three. The cause is still unknown, although in some cases they can be passed down genetically. The main features of ASD typically start to develop in childhood, although the impact of these may not be apparent until there is a significant change in the person’s life, such as a change of school.
In terms of broad classification, childhood Autism forms the core of the ASDs with its variants. Asperger syndrome could be considered to be closest to Autism in physical signs and likely causes. A major difference between Autism and Asperger syndrome is that there is no significant delay in language development in the latter. Another term used is Atypical Autism when the criteria are not met for a more specific disorder in this spectrum; it is also called as Pervasive Developmental Disorder-Not Otherwise Specified (PDD-NOS). Let’s look at each of these types in more depth.
Children with Autism are essentially considered to have problems in the development of their thinking, language, behaviour and social skills. These are usually noticeable before the age of Three, and can be diagnosed by 18 months especially if their siblings had similar issues. People with Autism can also have a learning disability, ranging from those requiring minimal support to lead an active life through to those requiring lifelong, specialist support. Although having a learning disability is not essential for diagnosis. For a diagnosis of Autism, a child must have a specified number of symptoms in the following areas:
- Social interaction
- Communication (including language delay)
- Restricted range of behaviours, activities and interests (often called stereotypic behaviours)
Asperger syndrome is characterised by the same type of qualitative abnormalities of reciprocal social interaction as in Autism, together with a restricted, stereotyped, repetitive repertoire of interests and activities. The main difference is in the fact that there is no general delay in language or in cognitive development. It is often associated with marked ‘clumsiness’ and tendency for the symptoms to persist into adolescence and adult life. Children with Asperger syndrome may find it hard to read the cues that other people give, such as facial expressions, body language and tone of voice. This would in turn make communication and interaction difficult leading to anxiety and/or confusion. Their interests can focus on one area to the point of obsession. They are reported to have average or in many, above average intelligence and this is the reason it is sometimes called ‘high-functioning autism‘, or that it is like a ‘Non-verbal Learning Disability‘ (NLD).
Pervasive Developmental Disorder-Not Otherwise Specified (PDD-NOS)
A milder form is called Atypical or Mild Autism, or Pervasive Developmental Disorder-Not Otherwise Specified (PDD-NOS). This refers to those people who have difficulties in more than one area but do not fulfil the diagnostic criteria for Autism or Aspergers syndrome. To have this diagnosis, all other possible diagnoses should be thoroughly assessed and eliminated. As is true with all diagnosis of exclusions there are concerns that they may be overused specially in children with behaviour issues. There is a definite need for more research to look into the possibility of positive criteria for PDD-NOS being developed.