What are pervasive developmental disorders (PDD)?

Introduction

Defined by a marked impairment in socialization, communication, and sometimes sensory integration, autism spectrum disorder (ASD) is a diagnosis introduced in the fifth edition of the
Diagnostic and Statistical Manual of Mental Disorders
(DSM-5). It encompasses the previously separate diagnostic categories of autistic disorder, Asperger's disorder, childhood disintegrative disorder, and pervasive developmental disorder-not otherwise specified. Clinicians had long had difficulty distinguishing among these categories, and there was insufficient research to support maintaining them as separate diagnoses.

Autism spectrum disorders are thought to have a biological basis. One of the strongest associations is with genetics. ASD generally has a familial linkage and researchers have begun to identify combinations of genes responsible for the conditions. Pre- and perinatal disruptions have also been implicated in causing ASD. Research suggests that being born very prematurely, being exposed to viral infections in utero, and experiencing oxygen deprivation during the birth process can increase the likelihood of developing ASD. The notion that ASD is caused by vaccinations has been refuted by research.

ASD is usually diagnosed in children around three or four years of age. Some children with autism show signs of developmental issues throughout their infant and toddler years, while others develop in the expected manner at first, but then slow or even regress. Symptoms typically include deficits in using and understanding language and difficulty relating to people and events. Symptoms also include unusual play with toys and other objects and difficulty with changes in routine or surroundings. In some cases, children exhibit repetitive body movements or behavior patterns. Unusual responses to sensory information, such as loud noises and lights, are also common. The condition typically remains with the individual throughout his or her life, although the course of the disorder can improve with early behavioral intervention. For individuals with ASD, an applied behavioral intervention strategy known as discrete trials has been successful in improving functioning. Individuals with high-functioning autism can often lead successful lives, although the impairments in socialization and communication continue throughout their lives. Children with ASD can have intelligence test scores that range from profoundly retarded to gifted. Although rarely seen, autistic savants can display extraordinary talents in select areas such as painting, counting, and memory. These individuals, however, often display intelligence quotients (IQs) in the mental retardation range. Raymond Babbitt, the main character from the film Rain Man (1988), is a good example of an individual with autistic savant skills. Raymond was able to count cards and remember events when provided with a specific date but was otherwise incapable of caring for himself or even providing correct change to purchase a candy bar.

Diagnosis

Individuals with ASD tend to show symptoms in two distinct areas. The first is deficits in communication and social abilities. People with ASD may have difficulty reading tone or body language, tending to take everything said at face value. They may not initiate conversations and may have difficulty sustaining a conversation once started. Often, they avoid eye contact and are uncomfortable with physical contact. They may also struggle to understand how other people feel or the reasons for their feelings. As a result, people with this disorder often have difficulty forming and maintaining interpersonal relationships.

The second category of characteristic symptoms is restrictive repetitive behaviors, interests, and activities, or RRBs. A person with ASD may have an extremely strong interest in one narrow subject and might talk about it constantly even if those to whom he or she is talking do not show any interest in it. Some autistic people may repeat a single word or phrase over and over or make repetitive nonverbal noises. They may also display repetitive physical behaviors, such as rocking back and forth or flapping their hands. Finally, they may be especially sensitive to sensory input of various kinds. The ways in which this sensitivity manifests vary among individuals, but some examples include being upset by loud noises, being bothered by particular clothing textures, and being a picky eater.

Severity of symptoms is classified according to a series of levels: Level 1, or requiring support; Level 2, or requiring substantial support; and Level 3, or requiring very substantial support. Individuals with mild, or Level 1, symptoms are usually able to attend school alongside neurotypical children their age, hold down jobs, and generally care for themselves. Meanwhile, those with more severe, or Level 3, symptoms may be unable to speak or perform basic self-care tasks and as such may require care throughout their lives. The two groups of symptoms are classified separately, so someone might have, for example, Level 2 difficulties with social behaviors but Level 1 RRBs.

Prevalence

As of 2007, the prevalence of ASD was estimated to be six cases per one thousand people. These rates have been found to be consistent across cultures and ethnic groups. However, they vary greatly by gender; on average, women and girls make up roughly one in four diagnoses of ASD, according to a 2009 study. ASD has, therefore, traditionally been considered to appear more frequently in males than in females, but more recently it has been proposed that females with ASD are underdiagnosed because they display different symptoms from males. ASD is often comorbid with other disorders, including epilepsy, intellectual disabilities, learning disabilities, and sensory processing disorder.

Controversy

The combination of the various disorders formerly categorized as pervasive developmental disorders into a single diagnosis in the DSM-5 has attracted criticism. Some of this criticism comes from people formerly diagnosed with Asperger's syndrome (a form of ASD without language development or cognitive delays), who feel that being considered autistic will increase the stigma against them. Another concern that has been raised is that the new criteria for ASD will make it more difficult to diagnose people whose symptoms are on the milder end of the spectrum.

Conclusion

Children with pervasive developmental disorders display impairments in communication and socialization, and often display stereotyped behaviors such as hand flapping, rocking, and intense interest in objects. The course of an autism spectrum disorder does not remit, although early intervention can improve social and communicative functioning. Individuals with severe versions of the disorder often require lifelong care. Higher-functioning individuals can often function independently and lead vocationally productive lives. Treatments for individuals with ASD usually involve behavioral therapy augmented by selected psychotropic medication. The cause of ASD is thought to be genetic, although researchers have not yet uncovered a definitive cause.

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