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Developmental Disabilities in Adults are Difficult to Understand and Detect

Kazuyuki Sakatsume
Professor, Faculty of Education and Integrated Arts and Sciences, Waseda University

Do an increasing number of adults suffer from developmental disabilities?

Recently, developmental disabilities in adults have been discussed on various occasions. At the student guidance offices of many universities, an increasing number of students have sought advice from counselors as they were suspected of suffering from developmental disabilities. These chronic conditions have often become a topic of conversation at workplaces, too.

Experts point out that the increase in developmental disabilities is associated with factors such as (1) an increase in the number of children with developmental disabilities (it is unknown whether the number is truly increasing and what their cause is), (2) a deeper understanding of developmental disabilities in society (this does not necessarily mean that a correct understanding of the conditions has become widespread), and (3) changes in the criteria for diagnosing developmental disabilities (doctors have come to consider that there is a spectrum of conditions between developmental disabilities and healthy development, and this often results in careless diagnoses)2).

Developmental disabilities in adults as seen from the viewpoint of behavior

Many adults with developmental disabilities notice them when they become adults. One characteristic of adults with developmental disabilities is that their intellectual faculties are not impaired. In general, they can act appropriately in daily life, but on some occasions in social settings, they cannot. For this reason, their behavior easily becomes incoherent. People around them characteristically tend to see that the inconsistency of their behavior is conspicuous.

One survey indicates that adults with developmental disabilities are characterized by their inability to make use of somebody’s kindness, understand the course of events, or manage personal relations, their tendency to throw cold water on what somebody is saying, or their inconsiderateness, arrogance, selfishness, inflexibility, or indifference. Previously, these behavioral characteristics tended to be considered as personality issues. The recent trend is that these people are suspected of having developmental disabilities (autistic spectrum disorders and attention deficit hyperactivity disorder).

Developmental disabilities in adults as seen from the viewpoint of higher brain functions

Figure 1: Relationships between Behavior/Ability/Function, Disabilities, and Support (Quoted from Bibliography3) by Modifying It)

The behavioral characteristics of developmental disabilities are related to the workings of the brain (see Figure 1). The latest edition of the American Psychiatric Association’s Diagnostic and Statistical Manual of Mental Disorders (DSM-5; the Japanese version was published in 2014) renamed developmental disabilities “neurodevelopmental disorders.” As shown by the disease name after the renaming, developmental disabilities are caused by problems that arise in the workings of the brain as nerves develop. It is necessary to understand developmental disabilities from the viewpoint of brain functions.

Functions such as speech, attention, recognition, and memory are called higher brain functions. They are related to different areas of the brain (cerebral cortex). In these areas of the brain, nerves mature at different speeds. The speed of nerve maturation is slowest at the frontal lobe (frontal association area). Developmental disabilities in adults see problems easily arise in the higher brain functions related to the frontal lobe where nerves mature slowly.

Higher brain dysfunction after injury to the frontal lobe often involves disabilities in executive functions, working or prospective memory, restraint, attention, emotion, and willpower. If executive functions are disabled, thinking and acting become unorganized and inconsistent. Disabilities in working memory prevent several kinds of information from being processed properly, and too much information confuses thinking. People that suffer from prospective memory disorders cannot keep their appointments because they cannot recall at the right time what they have memorized. In restraint disorders, they are unable to restrain themselves, with their behavior easily affected by the people around them. Conspicuous in attention disorders is a lack of concentration and endurance. A lack of emotional changes and the expression of strong emotions are observed in emotional disorders. Disabilities in willpower are marked by a lack of activeness and positiveness. Developmental disabilities are not always accompanied by brain damage, but difficulties similar to those brought on by brain damage are often observed.

Developmental disabilities in adults and mental agony

Up to now, developmental disabilities in adults have often been overlooked. However, developmental disabilities themselves are found even among children. Children with developmental disabilities easily cause friction with those around them, continuing to experience various kinds of mental agony (anxiety, frustration, and depression) into adulthood. During childhood, such mental agony manifests itself as the act of giving up too soon. Subsequently, the results of comparison with others and reflection are internalized as low self-esteem. Some individuals are troubled by the identity of their agonizing self (others are indifferent to their sufferings). Prolonged mental agony easily causes chronic fatigue, insomnia, compulsive behavior, PTSD, eating disorders, alcohol dependence, and the like. Having an understanding of such mental agony is also vital.

Support for developmental disabilities in adults

Figure 2: Types of Support (Quoted from Bibliography1))

Japan ratified the United Nations Convention on the Rights of Persons with Disabilities in 2014. The Act concerning the Promotion of Elimination of Discrimination on the Basis of Disabilities, which is effective in 2016, defines undue discriminatory treatment and lack of reasonable accommodation as discrimination and prohibits them. Reasonable accommodation refers to making changes or adjustments or providing services taking into account factors such as the degree of disabilities, gender, and age in order to offer equal opportunities to people with and without disabilities. This principle is applied to all areas such as health care, education, and the administration of justice.

Adults with developmental disabilities can be supported in various ways (see Figure 2). It is more important to help them attend school and adjust the working environment taking into account the characteristics of their higher brain functions and their mental agony than to directly improve the higher brain dysfunction they suffer from. Examples include providing general knowledge of developmental disabilities, encouraging them to have a positive self-understanding, guiding them in how to supplement abilities they are weak at and how to make the most of tools, correcting errors and biases in their unhealthy ways of thinking and acting, compiling manuals for problem-solving, educating people involved with them so they can have a deeper understanding, establishing natural support systems, securing counselors and supporters, and providing places for emotional support (organization and participation of peer groups).


^ 1) Kazuyuki Sakatsume, An Introduction to Neuropsychology, Which Displays Its Ability in Special Needs Education, Gakken Educational Publishing, 2011
^ 2) Kazuyuki Sakatsume, “A study of Increase in Developmental Disabilities and Their Feared Causes—Changes in Diagnosis, Social Acceptance, or the Fetal Environment?,” Waseda Review of Education (Bulletin of the Institute for Advanced Studies in Education, Waseda University), 26 (1): pp. 21–31, 2012
^ 3) Kazuyuki Sakatsume, Understanding of and Support for Disabilities Found in Developmental Disabilities and Cognitive Impairment, Journal of the Japan Health Medicine Association, 21 (2): pp. 50–55, 2012

Kazuyuki Sakatsume
Professor, Faculty of Education and Integrated Arts and Sciences, Waseda University

[Brief history]
Prof. Kazuyuki Sakatsume was born in 1957. He graduated from Waseda University with a bachelor’s degree in educational psychology. He completed the master’s course in psychology at Waseda University Graduate School of Letters, Arts and Sciences and withdrew from the doctor’s course at Waseda University Graduate School of Letters, Arts and Sciences after earning the required number of credits. After working as a research student in neurosurgery at Hamamatsu University School of Medicine, research fellow of the Japan Society for the Promotion of Science, chief at the department of psychology at the Kakeyu Misayama Rehabilitation Center Kakeyu Hospital, head of the rehabilitation guidance section of the department of rehabilitation at the Hamamatsu City Medical Center for Developmental Medicine, assistant professor at Urawa Junior College's Department of Welfare, and assistant professor at Senshu University's School of Law, he became a professor at Waseda University Faculty of Education and Integrated Arts and Sciences, the post he currently holds. He is a doctor of medical science.

Clinical psychologist, speech therapist, and clinical developmental psychologist

Japan Society for Higher Brain Dysfunction (delegate and member of the editorial board), Neuropsychology Association of Japan (councilor), Japanese Association for the Study of Developmental Disabilities (councilor), Japan Health Medicine Association (director and member of the editorial board), Kanto Society for the Mental Health of Children (director), Japanese Society of Pediatric Psychiatry and Neurology, Japanese Psychological Association, Japan Society of Developmental Psychology, Association of Japanese Clinical Psychology, Japanese Association of Rehabilitation Medicine, Cognitive Rehabilitation Society (manager and member of the editorial board), Japan Society for DOHaD (secretary) and others

His major writings include The Psychology of Higher Brain Dysfunction, Assessments and Case Studies of Developmental Disabilities That Can Effectively Be Used for Special Needs Education, An Introduction to Neuropsychology, Which Displays Its Ability in Special Needs Education, How Can Brain Science Be Used for Education Effectively?, Thinking about Eating, Development, and Health, Thinking about Impetus, Delinquency, and Crimes, How Should We Approach Development Disabilities?, Rehabilitation of Higher Brain Dysfunction, The Development of Children and Brain Science, Reasonable Accommodation for Persons with Mental or Developmental Disabilities, and Guidance in Language in the Period of Inclusive Education Systems.