Many attempts have been made to explain autism spectrum disorder (ASD) as a unified theory [1,2], but the expression patterns of ASD are very diverse. Although many people are familiar with the categorical approach that individuals with ASD are distinctly different from neurotypicals, experts are also aware of the dimensional approach to understand psychological and behavioral characteristics in a continuous line between neurotypical and autistic aspects [3,4]. Individuals with ASD have their own strengths. For example, people with high autistic tendencies have a high ability to “systematize” [5].

Therefore, intervention on target symptoms is important when establishing treatment strategies for individuals with ASD, but more importantly, the goal should be to establish “niche construction” [6] where they can demonstrate their characteristics and strengths. In other words, uncomfortable sensory stimuli in treatment rooms and education spaces should be minimized, and prior stimuli should be adjusted in various intervention situations, which should vary depending on either the developmental stage of the person with ASD or the family’s situation. In addition, it must be emphasized that the treatment and intervention of individuals with ASD should be appropriately performed according to the life cycle. This is not necessarily a task. Many recent studies are proving that much more could be done to improve life outcomes for the highly heterogeneous group of people with ASD [7].

Therefore, the authors intend to present the general principles of treatment for individuals with ASD and the principles of intervention strategies for each life cycle through this review.

There is much research on the effect of ASD intervention, but most of them did not have control groups or consider different kinds of bias. In recent years, randomized controlled trial (RCT) studies have been increasing [8], but only a few RCT studies have been conducted on individuals with ASD in Korea [9]. In addition, there is a lack of data on the provision of step-by-step treatment services according to the life cycle. Therefore, this guideline not only provides information with proven treatment and intervention effects with RCT as much as possible, but also refers to additional information from evidence-based research results, even if randomized controlled methods were not applied to these research, mentioned in authoritative academic societies, journals, and foreign guidelines. To communicate practical knowledge for the individuals with ASD and their families, the following eight general principles are recommended.

The planning and implementation of all treatments should be carried out differently and most appropriately depending on the characteristics of each person with ASD

The causes and manifestations of ASD are so heterogeneous that there is no single treatment that is equally effective for all. “Customized” treatment interventions and social support should be made in consideration of the diversity of manifestation, differences in social skills, differences in strengths and interests, and the environment surrounding the individual.

Start treatment as early as possible

Due to the characteristics of parenting in Korean caregivers, there is a kind of irrational expectation of “Let’s wait for now” even though the development of their sons and daughters has been delayed. However, other developed countries do not have this kind of phenomenon at all. Some doctors also make similar recommendation [10]. In recent years, young caregivers’ observation level and desire to intervene in early treatment for children who are slow to develop are increasing, but some doctors or experts in Korea, who are more familiar with past “Diagnostic and Statistical Manual of Mental Disorder (DSM)” system, are rather passive in early treatment of toddlers or pre-school-age children who are strongly suspected of ASD. There are many research reports that children suspected of ASD acquire a much higher level of skills through early intervention [11,12], so early treatment and intervention are essential if any findings suggest ASD were found through early evaluation.

Through pre-treatment evaluation, determine which treatment and intervention will be useful

After evaluating medical problems accompanying ASD (e.g., epilepsy, etc.), characteristics of temperament, behavioral problems, and current developmental levels, it is necessary to determine which treatments and interventions will be useful. In particular, an accurate functional assessment of the capabilities of the individuals with ASD should be included. In addition, family situations and treatment-related environmental factors should be considered. The medium and longterm goals of intervention must also be determined in advance. In addition, an evaluation method that can monitor how much outcome the person with ASD has obtained through treatment intervention should be determined.

Consider the strength and generalization of treatment and intervention

It is recommended to refrain from multiple interventions that are sporadic or end in a short period of time [13]. It is also necessary to avoid setting the number of treatment sessions in advance and matching them. Treatment and intervention methods should be systematically performed, even if they proceed in different formats, and the effect should be maximized through communication between the personnel of each treatment and intervention as much as possible. In addition, it is not significant to have an effect only in a structured environment. In other words, generalization, which continues to be effective in real life, must be achieved.

Both the strengths and weaknesses of the ASD parties are considered, but the treatment is selected in consideration of the strengths

Because the treatment and intervention strategies of individuals with ASD vary depending on the age, developmental level, and environment, individual strength-related and weakness- related characteristics should be closely examined. In particular, experts in deciding treatment and intervention method should discover strengths that the parties and caregivers have not seen before, rather than focusing only on weaknesses such as symptoms or behavior problem of the individuals with ASD, and choose appropriate treatments.

Focus on making the environment friendly to each person with ASD

Creating a friendly environment for each person with ASD is very important because unusual sensory experiences are so common that 69%–93% of them are reported to show excessive sensitivity to hearing, sight, taste, or other sensation [14]. Considering this high frequency, it may be right to view sensory characteristics not from the perspective of “problem symptoms” but from the perspective of “kinds of characteristics that can be a strength in a comfortable and friendly environment.” Through appropriate changes in the environment surrounding them, they will be able to acquire their own “niche construction” [6] and maintain their emotional stability for a long time.

If possible, establish an evidence-based, multidisciplinary treatment plan

Several guidelines for ASD recommend an evidence-based, multidisciplinary treatment model [10,15,16]. In other words, in addition to structured educational and behavioral interventions, psychosocial interventions in the form of cognitive behavioral therapy can be effective for high-functioning individuals with ASD. Meanwhile, psychopharmacological intervention can be effective in accompanying emotional problems, excessively stereotypic behaviors, sleep problems, aggression, and self-mutilating problems. Experts should recommend evidence-based multidisciplinary treatment plans to the parties and their caregivers as much as possible, but at the same time, recommend treatment plans that take into account individual family and environmental situations.

Work together with the individuals with ASD and their families

Although clinical experts establish a number of effective treatment plans, the final decision makers are the individuals with ASD and their families. The family should be fully aware of information on various treatments and interventions and the practical effects of each intervention. Each family has its own circumstances. Therefore, if a treatment plan requires a serious change in their inherent situation, it should be corrected. Meanwhile, there are several conditions to consider when deciding to actively participate in treatment; for example, whether it is possible to enough time for treatment intervention in situations where school needs to be maintained, whether there is a support system to alleviate financial difficulties for various treatments, and what are the advantages of national disability registration. In response, clinical experts should be well aware of relevant information well and provide appropriate advice.

Infancy and toddlerhood

When children are diagnosed with ASD, their caregivers often get puzzled because they do not understand what it means [17]. In such cases, clinical specialists should provide psychoeducation to demystify the disorder and other details, including its causes, clinical manifestations, prognostic factors, and treatment methods, for the family. They must also introduce available resources, such as guidebooks, leaflets, and credible websites of relevant organizations, to help the patients’ caregivers understand ASD comprehensively [18]. When making treatment plans, the focus should not only be on defects and disorders in the individuals with ASD but also on customized intervention strategies by comprehensively examining the strengths of children, areas of development at a relatively normal level, and the areas of interests and available resources in the family, following the evaluation of children based on the normal developmental trajectory [8].

Interventions should be based on the evidence, and good prognosis can be expected by administering interventions as early as possible [19]. Interventions must target the core symptoms of ASD, including defects in social communication and interaction, limited interests, unique rules, stereotyping, and sensory information processing abnormalities, in addition to the derived emotional, adjustment, and behavioral problems. Diverse treatment methods are combined for each of the symptoms [20]. For infants and toddlers in particular, the focus should be on improving basic functions, including eye contact, naming response, mimicking, joint attention, demanding, language skills, and play skills, which can be intervened in structured and natural environments. In a structured environment, behavioral intervention specialists work with children on a one-on-one basis for their education; the same intervention principles can be applied to various situations in everyday tasks, including mealtime, playtime, and bed time, to generalize the function. The participation of the entire family is essential in this stage; the family should be diligently trained under the supervision of behavioral intervention specialist [8].

Prior to being diagnosed with developmental disorders, individuals with ASD have the same needs as those of the same age but without any disorders; thus, ordinary circumstances should be provided, including secure attachment, balanced meals, and good sleep quality [10]. In the individuals with ASD, comorbidities occur frequently, including gastrointestinal disorder, sleep disorder, metabolic diseases, and dental diseases, which should be appropriately addressed [21]. They also have the right to various educational benefits and to experience a broader world; therefore, it is necessary to make adjustments in communication, social, and physical environments relevant to children [17].

The families of these children may experience serious stress due to challenging behaviors and emotional outbursts in the individuals with ASD, the collapse of family life, discomfort and alienation of siblings, financial difficulties, physical and mental weakness, conflicts between caregivers, and the absence of information and resources [22]. Therefore, this should be intervened as well. In addition, the relevant information should be provided to allow access to all support services, including developmental rehabilitation services, disability registration, support services for people with developmental disorders, special education support services, and self-help groups or family meetings in local communities, such that the families can have psychological stability and be in a state support their children [23].

School age period

When the individuals with ASD reach the age to attend kindergarten or school, education allocation problems may be encountered. Similar to individuals with disabilities education improvement act (IDEA) in the United States, the Act on Special Education for Disabled Persons stipulated that the individuals with ASD must receive integrated education in a regular school with other persons of the same age which is suitable for the educational needs of each individual without any discrimination [24]. Their families want their children go to these kinds of school; however, regular teachers rarely receive the specialized education to effectively manage the individuals with ASD [25]. Therefore, partly inclusive schools that run regular and special classes together or special schools can be realistic alternatives for the individuals with ASD and their families. For inclusive education, the individuals with ASD can have the opportunities of social interaction and develop the generalization ability with which they can apply the acquired skills in everyday environments. Conversely, devoted special education is beneficial to children in whom an expansion of such skills is not expected yet owing to developmental levels, severity of symptoms, and challenging behavioral problems. However, there is no evidence to indicate that certain types of education services are superior to others [10]. Nonetheless, when a family chooses a schooling system, it is recommended that they make a decision after consulting a special education specialist rather than making an arbitrary decision or referring to a layman’s advice.

It is important for special classes and schools to have welltrained specialists who can cater to the children’s needs as per the individual characteristics of the individuals with ASD and the ages of development, as well as a special environment to implement it. It is necessary to prepare a program promoting socialization and linguistic development, and adjust visually and acoustically stimulating environments by considering sensory characteristics in children [23]. A universal design can be applied to all school environments so that anyone can use facilities easily, understand the timetable, participate in various activities, and communicate smoothly using visual materials [20]. For example, for children whose stereotypic behaviors become more serious when they feel anxious because they do not know what will happen, a timetable can be made using photos and pictures to let them know the next schedule, which can reduce their stereotypic behaviors and help them adjust to the environment.

It is often noted that the individuals with ASD show low academic performance, and have difficulties in relationships with teachers or peers of the same age, which mainly attributed to a lack of social skills and their internalizing, and externalizing behavioral problems [25]. A good relationship with teachers is essential for the individuals with ASD to successfully learn skills, perform behavioral adjustment, acquire social skills, and form good peer relationship; therefore, education service providers should consider this [26]. Moreover, teaching staff should recognize that the individuals with ASD are at high risk of exploitation and bullying [27] and should educate students on self-identity, how to protect themselves on the internet, how to recognize and report bullying, and how to improve self-esteem [10]. After reaching puberty, the individuals with ASD may expose their body, masturbate, get excited inappropriately in public places, or be sexually abused; specialized sexual education is needed to prevent this [28]. Teachers should educate them about the names and functions of each body part, the physical maturation process, socialized sexual behaviors, managing sexual urges, and protecting themselves from sexual abuse.

The child’s family must recognize such difficulties in the individuals with ASD in advance and be prepared for some of these challenges before the children are admitted to schools. It is advised that children have training for basic living habits including how to use a bathroom, eating a variety of foods, how to put on and take off shoes. Their families should organize information about the children to give to their teacher and train children to get along with neighborhood children who are going to attend the same school, thus preparing the ground for adjusting to a new environment [23]. Furthermore, teachers should identify clinical symptoms and characteristics of each individual as well as comorbidities for better understanding the individuals with ASD. To this end, it is recommended to periodically communicate with clinicians. If they can seek advice and request interventions for various comorbidities, including incomprehensible behaviors of the individuals with ASD that are commonly observed in education fields, in addition to depression, anxiety disorder, attention deficit hyperactivity disorder, epilepsy, and gastrointestinal disorders, they can help children more effectively.

Transition to adulthood

Studies have shown that many individuals with ASD cannot be independent, make friends, and find employment at a good company paying a good salary; this makes them dependent on their family [29]. The core symptoms of ASD last in the transition period to adulthood [30]; thus, speech therapy, occupational therapy, and training for social skills may be needed. Other than that, for smooth independence, it is necessary to provide self-management skill training, living skill training, occupational skill training, and one-on-one support services, including career and employment support, mentoring program, case management, and mental health counseling; however, there is a lack of available resources involved in this. This is because of the services cliff phenomenon that occurs: the types of support required are different from those of childhood but there is a lack of transitional programs that can intervene at the period of the transition to adulthood as well as a lack of experts, systems, and budget such as government expenditure and fund [31-33].

Nearly 50% of the individuals with ASD develop cognitive abilities within the normal scope [34]; thus, they can go to college when they become adults, but it is not easy to have a successful college life. They are used to a fixed routine, making it hard for them to adjust to a complicated curriculum. Moreover, due to a lack of social skills, they cannot blend into an expanded organization [25]. Colleges also provide the support for learning, such as extending the time for examinations, putting off a deadline for assignment submission, and giving options for group activities. Besides that, however, they do not provide customized supports considering individual characteristics of students [35,36]. The employment landscape is also not friendly for the individuals with ASD, making them more isolated from the society and leaving them feeling depressed and anxious, which may lead to a suicide attempt [37,38]. Therefore, the individuals with ASD and their families should be prepared for such realities [39]. In other words, families, teachers, and specialists should meet together to choose a school, a college major, or job based on the functional level of students, strengths and weaknesses, areas of interests, and goals. They should also find services necessary to achieve this and organizations providing these services. In addition, they should help students to improve their interpersonal relationship skills, problem solving skills, decision making skills, and time and stress management [40,41], and identify companies they want to work for, obtain necessary qualifications, and practice interview skills [28].

Adult life

The life expectancy of the individuals with ASD is not clearly known; except for cases of deaths due to accidents or physical diseases, they can have normal life expectancy [42]. Therefore, they live as adults for most of their lives, want to realize their goals, expectations, and interests in the context of culture and value systems, and live a satisfactory life. Accordingly, World Health Organization has added nine autism- related items to the “Quality of Life” measurement tool, emphasizing that achievement of high quality of life is a goal of all adults including the individuals with ASD [43].

Generally, social support alleviates stress and improves a sense of belonging and self-esteem; thus, it is a crucial factor influencing the quality of life [44]. Despite the common misconception that they prefer being alone, the individuals with ASD can feel intensely lonely because of businesslike relationships that lack intimacy, reciprocity, and emotional fullness [45]. Therefore, the evidence-based interventions are still needed to improve social functions when the individuals with ASD become adults.

A stable job in which appropriate wage is guaranteed is also an effective way of improving quality of life [46]. Quality employment environments alleviate the core symptoms of ASD, improve cognitive function, and help improve health and self-esteem [37]. Moreover, it enables financial independence, enhancing an access to a comfortable residential environment and leisure activities [10]. Employment support comprises local community-based occupation allocation, support for seeking jobs and preparing for employment, and field support after employment [28]. Behavioral interventions, including modeling, rehearsal, feedback, and enhancement, can be attempted for skill training necessary to improve work ability and adjustment [28,47]. However, the most important aspect is an employer’s efforts to change the interview process and physical work environment to make them ASD friendly [10].

Considerations for a quality residential environment enable the individuals with ASD to be a member of the local community in a least restrictive environment [28]. Building a close relationship with neighbors, performing roles, and living on assistance reduce loneliness [10]. Furthermore, interventions for the above mentioned physical and psychiatric comorbidities and programs designed to develop leisure and everyday life skills can also improve quality of life [48]. A family should be considered an essential component of the treatment team, and family quality of life should be considered equivalent to quality of life in the individuals with ASD [49]. All these tasks remain challenging and will never be completed. Only the on-going efforts of many can lead to an improved and sustained quality of life for the individual.

In summary, based on the understanding of the individual characteristics of the individuals with ASD, the early implementation of individualized interventions that expand their strengths and eliminate barriers is the beginning of management. And the goal of management as they grow older is to help the individual with ASD to pursue happiness and independence by providing a disability-friendly environment suitable for their circumstances. A lot of resources are needed for this, but the work of cultivating a living ground for the individuals with ASD, their families, neighbors, and citizens to live together enhances the happiness and dignity of members of society, so the benefits ultimately belong to all of us.

Data sharing not applicable to this article as no datasets were generated or analyzed during the study.

Jung-Woo Son, a contributing editor of the Journal of the Korean Academy of Child and Adolescent Psychiatry, was not involved in the editorial evaluation or decision to publish this article. All remaining authors have declared no conflicts of interest.

Conceptualization: Jung-Woo Son, Seok-Hyun Nam. Formal analysis: Jung-Woo Son, Seok-Hyun Nam. Investigation: Jung-Woo Son, Seok-Hyun Nam. Methodology: Jung-Woo Son, Seok-Hyun Nam. Writing—original draft: Jung-Woo Son, Seok-Hyun Nam.

This study was supported by the Ministry of Health and Welfare, Behavior and Development Center, and the Headquarter of the National Autism and Developmental Disorder Centers.