A Comprehensive Guide to Symptoms of Autism Spectrum Disorder(ASD)
19 min · Special Needs
July 21, 2023

A Comprehensive Guide to Symptoms of Autism Spectrum Disorder(ASD)

Autism spectrum disorder has certain defining symptoms that make up the core of the disorder itself. We wanted to gather the core symptoms of ASD together in one article.

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Restricted and Repetitive Behavioral Symptoms of Autism Spectrum Disorder

In 1943, Autism was first described by psychiatrist Leo Kanner as a disorder seen in children who had communication problems and were highly sensitive to changes in their surroundings. The disorder appeared to be rare back in those days. It was differentiated from schizophrenia in that it was presented from birth. Compared to those days, according to the Centers for Disease Control and Prevention (CDC), the prevalence of autism spectrum disorder increased to one in 36 children , boys being 4.2 times more likely to be identified with autism compared to girls. This increase in autism spectrum disorder prevalence is partly due to the ever-evolving diagnostic criteria. Increase in general social awareness as well as the availability and accessibility of treatment also contributed to the boost in prevalence of the diagnosis. In addition, more school-aged children who are on the high-functioning side of the scale are being diagnosed with otherwise previously unrecognized ASD.

The 5th edition of Diagnostic and Statistical Manual (DSM-5) by the American Psychiatric Association gathered four disorders which were previously separated under one single diagnosis. These categories were autistic disorder, Asperger syndrome, childhood disintegrative disorder and pervasive developmental disorder, not otherwise specified. In diagnosis of mental and behavioral conditions like autism, DSM-5 is now the standard reference used by healthcare providers. In addition to the changes of the disorder categories, the guide also consolidated three previous categories of autism symptoms, namely the social impairment, language/communication impairment, as well as repetitive/restricted behaviors into two categories of symptoms, which are persistent deficits in social communication/interaction, and restricted, repetitive patterns of behaviors.


Restricted and repetitive behaviors (RRB) are core indicators of autism spectrum disorder. If a child presents certain behavioral patterns, such as repeatedly clapping hands and obsession, the clinician will probably diagnose the child with autism spectrum disorder. These RRBs are core diagnostic features of ASD. Individuals with autism may engage in certain stereotyped and repetitive movements or speech. These include ‘stimmings’ such as hand flapping, lining up items in certain order, or echolalia, which is repeating noises and sounds an individual hears. Individuals presenting restricted and repetitive behaviors, interests, and activities may insist on everything being the same. They may want to take the same route to school everyday, or complete certain routines in the exact same order each time. Restricted and repetitive behaviors may interfere with individuals’ lives by impacting their ability to socially interact with the world. Individuals with autism spectrum disorder may feel overwhelmed if their restricted and repetitive behavior patterns are disrupted, making them anxious and even aggressive. Research showed that in reducing of RRBs and other related problem behaviors associated to RRBs can be reduced with behavioral interventions.

Repetitive Behavioral Symptoms

Repetitive behaviors refer to abnormal behaviors that are generally characterized by repetition, inappropriateness to the situation as well as lack of adaptability. Motor stereotyped behaviors fall within this category and they include self-stimulatory behaviors, self-injurious behaviors, compulsive or sameness behaviors as well as verbal repetitive behaviors. Repetitive behaviors are also called ” stereotyped ” behaviors. These seemingly purposeless behaviors are a hallmark symptom of autism spectrum disorder.

Individuals with autism spectrum disorder may repetitively open and close drawers or ask about the same thing repeatedly. Repetitive behaviors may include hand flapping, finger flicking, rocking back and forth, and sometimes self-harming behaviors like head-banging. Individuals presenting repetitive behaviors also repeatedly use a single object . For instance, a child with ASD may constantly flick a rubber band or want to feel a certain texture. This behavior is also called ” stimming ”, a self-stimulating behavior.

Repetitive behaviors pose a problem when they occupy a major part of the individuals’ lives and get in the way of daily activities, like getting through the day at school. With advancement of technology, we have been able to obtain information as to why these repetitive behaviors occur. Previously thought to be aimless, such behaviors are discovered to be also a tool for self-calming for individuals with autism. Studies indicate that certain behaviors like rocking back and forth or waiving of the arm help guide typical development. Research done in the past decade reinforce the idea that repetitive behaviors help individuals with autism in overcoming the sensory overload as well as cope with anxiety. These behaviors are sometimes utilized to express how they feel.

Thanks to the advancements in technology , studies have been conducted for the past decade to figure out the reasons for these repetitive behaviors. It was found that these movements help individuals with autism to adjust the degree of stimulation they experience. This brought about a new perspective to repetitive behaviors encountered in individuals with autism spectrum disorder. Matthew Goodwin , Associate Professor of health and computer sciences at Northeastern University in Boston, Massachusetts decided to put his ideas into action. Goodwin and his team vested children and young adults with autism spectrum disorder with wearable technology consisting of heart-rate sensors. Through these sensors, they managed to track heart rate and other physiological signals. The participants were also recorded on video to track their repetitive behaviors through the day. Researchers found that there was a spike in heart rate of the participants before the stims. Goodwin explained that these repetitive actions might actually be helping individuals in managing the stimuli they receive from their environment. Some people may even be stimming intentionally, just to adjust to their environment. This would suggest that we should adopt a different approach to repetitive behaviors. In certain cases, taking these stims away from people with autism spectrum disorder may do harm than good. In addition to “normalizing” the environment for hyper-stimulated individuals, such stims are also a way to arousal of nervous system for understimulated individuals.

Repetitive behaviors can also cross over with other characteristics of autism spectrum disorder. One of these characteristics is intense preoccupation of individuals with certain objects or interests. For instance, children with autism may spend hours lining up their toys in a certain way and not use them to actually “play”. These children would be highly disturbed if one of the toy is moved or there is any slight change to their routines.

There are no specific treatment for repetitive behavior. Applied behavior analysis (ABA) is an evidence-based technique used to study and modify behavior. It is widely used effectively especially with individuals with autism spectrum disorder, as well as other developmental disorders. In this therapy method, the behaviors of the individual is observed. Their reactions to changes in their environment are analyzed. Through positive reinforcement, the behaviors are changed and new life skills can be acquired.

In addition to ABA, sensory integration therapy is also used. This therapy is also utilized for children on the autism spectrum disorder. They usually have issues with sensory problems and these may trigger these repetitive behaviors. Certain smells and textures, for instance, may result in outbursts in their everyday life. However, despite being used widely, it is not an evidence-based treatment.

Restricted Behavioral Symptoms of Autism Spectrum Disorder

Children with autism spectrum disorder may be fixated on one or two topics. They may have highly restricted, fixed interests that might be abnormal in terms of the intensity and focus thereof. This specific topic maybe the only thing that they want to talk or think about and concern themselves with. Children with autism spectrum disorder may be strongly attached or preoccupied with a certain object. This may make them want to have this object with them at all times.


Similar to the repetitive behaviors, restricted behaviors may disrupt everyday lives of the individuals. The fixation and limited interest in certain objects or topics may severely impact the individual’s life. The fixation caused by restricted behaviors usually prevents the individual from understanding the entirety of the situation. For instance, a child may focus on the rotating wheel at the park instead of playing with their peers.

In the past decades, researchers associated such restricted behaviors and intense fixations with good language and cognitive abilities. However, recent developments showed such restricted and repetitive behaviors can be found in most individuals across the autism spectrum. These are thought to help the individual relieve the overwhelming feeling they get when they are encountered with overstimulation. There is some evidence that males may be more prone to these behaviors. More and more research is being done on the gender difference in the autism spectrum disorder diagnosis. Some of the studies focus on identifying whether certain restricted and repetitive behaviors can distinguish girls from boys.

Social Symptoms of Autism Spectrum Disorder

Autism spectrum disorder is characterized by certain signs that usually present at a young age. However, people may not receive a diagnosis until adulthood. Physicians and specialists categorize autism spectrum disorder by assigning a level 1, 2, or 3 support based on the 5th edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5). Severity score is determined in line with both the impairment in social functions and the restrictive and repetitive behaviors.

Social symptoms include low tendency to make eye contact and smile at others. Children showing social symptoms are unlikely to imitate others’ actions like playing with their toys. They may also not really like or want to participate in games. It is difficult for children with autism spectrum disorder to engage in back-and-forth babbling or conversation with others. These individuals rarely initiates communication. They show lack of interest in sharing anything they have, even their experiences. Children on the spectrum disorder may even use others as a tool, like grabbing their hands or arms to take something they want without even looking at their faces. They may only establish contact when want to get things or help. Individuals diagnosed with this disorder may not notice others around them, preferring the solitude. Instead of playing with the toys like others do, children with autism spectrum disorder may exhibit restricted and repetitive behaviors like lining them up in a certain way instead of playing with them. Individuals on the autism spectrum may show expressions that do not really match the communication context. Children with autism spectrum disorder may discuss their interests in a detailed way due to also their limited and restricted interests. They may even exhibit unusual social interactions like smelling others. Children with ASD would show these indications generally by the time they turn 8 or 10. Individuals may not always show all of these social behaviors but these are some of the most common ones.

The stemming cause of the behavioral and social symptoms of autism spectrum disorder is still being studied. In a research conducted by a team of UCLA scientists in 2015, MRI imaging was used to study the brains of the participants consisting of 17 youths with high-functioning ASD and 22 typically developing children and adolescents. Researchers used the imaging technology to track their brain blood flow as well as the strength of connections within intrinsic neural networks. They were testing whether ASD might be caused by increased or decreased connectivity within specific neural networks that actually make up the “social brain”. Social brain is the network of brain regions that help us understand other people. It also includes the parts of brain that are key to the process of mentalizing. Mentalizing is attributing mental states to the person themselves and to other people. Individuals with autism struggle with many of the social aspects in their lives.

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The connectivity within the neural networks was measured through the amount of blood flow as well as the activity patterns called neural networks. When participants were scanned, it was revealed that there are significant differences between the two groups of people. In children with ASD, a pattern of widespread increased blood flow was discovered. This means that there was a hyper-perfusion of blood in the brain. This was linked to increased oxygen metabolism in the frontal brain parts, which are quite important in terms of managing social interactions. Generally, blood flow is reduced while a brain develops. The findings revealed in the study indicating a continuing hyper-perfusion in children with ASD suggest delayed neurodevelopment in these brain regions, which are linked to socio-emotional cognition. Researchers found that previous structural MRI findings suggesting enlarged brain size are aligned with this research as well. This shows an overabundance of neurons in individuals with ASD, due to synapses of neurons not sufficiently losing the excess blood while the brain develops. Excessive functioning synapses are proven to inhibit cognition and require extra blood flow. The research team also discovered that the long-range connectivity between the front and back of the brain in those with ASD was reduced compared to typical brains. This means that due to this loss of connectivity, information flow does not go how it should be between different and distant parts of the brain. This may explain impairment in social interactions. This approach was also used in other disorders related to brain, such as schizophrenia. It led to insights and alternative treatment approaches in this disorder.

It is difficult to assess the severity of specific symptoms. This assessment requires long evaluation and observations of the individual with autism spectrum disorder. Generally, questionnaires are done to assess the situation. However, this can be subjective. There are studies to provide an objective method to quantify the severity of certain core social symptoms of autism spectrum disorder. These studies utilize advanced technology such as motion capture system. Further development of this technology as well as appropriate use of motion capture measures are thought to improve the assessment methods for social ASD symptoms, as well as their change over time.

The treatment methods pursued by families are widely diverse due to varying presentation of the disorder in each person. They also depend on the age and developmental stage of the child. Treatment options range from behavioral interventions to various other complementary approaches. Treatments of ADS, it is aimed to alleviate the core deficits in child’s social communication and interactions to provide them a life where they can function independently. Although there is no cure for ASD, combinations of behavioral and education therapies as well as medical therapies help individuals combat the social and other symptoms that hinder their daily life. Among the most common treatment options are the behavioral approaches. Applied Behavior Analysis ( ABA ) is one of the few treatments proven by hundreds of studies to be effective for children with autism spectrum disorder. In ABA, psychological principles of learning theory are applied in a systematic manner to alter behavior in humans or animals. Positive effects have been achieved through these interventions in terms of social symptoms. Studies suggest that early intensive therapy may lead to great improvements.

Speech and Language Symptoms of Autism Spectrum Disorder

Impairments in speech, language, and social communication are categorized as the core symptoms of autism spectrum disorder. These are included in the primary diagnostic criteria for ASD. As manifestations of the disorder vary from one person to another, language abilities range from being nonverbal to idiosyncratic language with echolalia. Around 25% of individuals on the autism spectrum disorder never develop functional language skills despite receiving years of intervention. There has been a lot of changes in the definition of autism since the days of Kanner , but impairments in language skills remain striking features of autism spectrum disorder. In the new edition of Diagnostic and Statistical Manual of Mental Disorders (DSM-5), the three core symptoms, namely social interaction, communication and restricted behaviors specified in the previous version were reduced to only social communication and restricted/repetitive behaviors. This implies that social and communication skills are closely interwoven.


An individual with autism spectrum disorder may lose early words. Since they may use words non-traditionally, they may be difficult to understand. There is a condition called echolalia, where the individual may repeat some words or phrases they heard from someone, maybe even days or weeks earlier. The voices of an individual with ASD may be robotic or in a singsong manner of speaking. Sometimes they talk very little or maybe not at all. They may have extensive vocabulary but in communication, they may utilize challenging behaviors instead of words or gestures to communicate what they want. Most of the individuals with autism spectrum disorder have issues in terms of both receptive and expressive language.

Difficulties in social skills or language are generally the root of communication problems in children diagnosed with ASD. Their ability to use language boils down to communicating only when they want something. They have difficulty in using the language to comment, request information or describe what is going on. Children with autism spectrum disorder present atypical responses in terms of receptive language. They may be disoriented in their speech, and may not respond to their name when they are called. This occurs by the age of 6 to 12 months. All of these indicate issues in receptive language problems. Comparatively to other neurodevelopmental disorders with relation to language, children with autism spectrum disorder were found to have a significantly greater impairment in their receptive language. Therefore, the development of receptive ability over expressive is substantially reduced for the individuals with autism spectrum disorder.

Speech and language skills of many children with autism spectrum disorder usually develop unevenly. Their progress generally do not reach a normal level of ability. While they may develop robust set of vocabulary skills in the area they are interested in very quickly, some children may not be able to do that. Some children with ASD can remember what they just heard or seen very well. Others may be able to read some words before they reach the age of five, but not entirely understand or comprehend what they read. Individuals with autism spectrum disorder generally do not respond to what others say, or reply when their names are called. Due to this fact, some children are mistakenly thought to have a hearing problem.

In the event that a doctor thinks that a child may have autism spectrum disorder, they refer the child to specialists. Speech-language pathologists are one of these specialists. In this line of profession, the specialists are trained to treat individuals with voice, speech and language disorders. After comprehensive evaluation of the child’s language-speech developmental level, the specialists will also look into the child’s ability to communicate. Then, they will design an appropriate treatment program for the child.

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Improving speech and language skills of a young child is achievable. The process needs the attention of caregivers of the child. Children begin communicating before they acquire the skill of language. They babble, imitate and make eye contact and body movements. Caregivers should be careful to observe these behaviors and consult to speech-language pathologists if they see any delay. Through communication training, children diagnosed with ASD may acquire basic speech and language skills. Some children with ASD may never learn speech or acquire any language skills. Here, the goal could be learning to communicate through other ways. This may be using gestures like the sign language. Or picture boards or cards to electronic devices and apps that generate speech through AAC may also be utilized.

Nonverbal Communication/Social Interaction Symptoms of Autism

Many individuals with autism have delays or difficulties in their speech. Although autistic individuals have generally difficulties in talking or engaging in a conversation, nonverbal individuals are not able to talk at all. Around one third of individuals diagnosed with autism are considered nonverbal . This means that they don’t speak or speak only a few words. According to CDC , 40% of children with ASD don’t speak at all (Note that numbers are not current but general). Despite the number of nonverbal individuals diagnosed with autism, the term “nonverbal” is not an official diagnosis. One of the reasons for this is that there is no clear distinction between verbal and nonverbal individuals with autism.

Use of language differs from one individual with autism to another. Some may be able to use a few words in a meaningful manner. They may convey what they want or call someone’s name. They may say “water” to imply that they are thirsty. But it is difficult for them to carry out conversations. For instance, they may not be able to answer the question “would you like a glass of water?“.

Speech and communication are different things. Some individuals with autism who are nonverbal may have the ability to speak. But they may be unable to use language in a “natural” and meaningful manner. They may use what they learned from their speech therapist, or something they heard from their parents repeatedly. This is some sort of self-soothing way for individuals with autism. Although they are sometimes unable to utilize spoken language effectively, some of the nonverbal individuals with autism may use written or typed language, picture cards or more often than not, digital communication devices like AAC.

In general, most of the individuals with autism struggle with social interactions. They are not good at the natural and mutual communication and interaction. Speech and social interaction are often particularly difficult for them. And since it is difficult to understand them, others may find challenging to interact with them. This creates a double challenge for both parts. There are various reasons as to why this happens. Individuals with ASD may have different verbal abilities. This ranges from no speech at all to speech that is somewhat fluent but often inappropriate. Also, people with autism use speech in idiosyncratic manner. Also, spoken language is not the only way to communicate and often not enough. People use various other things to communicate. People use our body language like making eye contact or hand gestures. While talking, it is common to use pragmatic language or adjust the tone of the conversation to what is appropriate. People also make use of idioms and slangs.


It is also important to determine which type of speech is appropriate to the setting. These are all of the things individuals with ASD struggle as is. They often avoid eye contact and only interact to achieve a specific goal. People with ASD may not understand other people’s feelings, so they may raise their voice when it is not the appropriate tone at that particular setting. They find it challenging to use or understand non-verbal cues like hand gestures or the tone of the voice. One of the signs of autism is that people may speak in flat, sing-song voice about topics they are interested in.

Aside from childhood apraxia of speech, which is a neurological disorder that speech difficult, we don’t quite know why people with ASD don’t speak. Some nonverbal individuals use American sign language or picture cards to communicate but don’t speak. However, this doesn’t mean that a nonverbal individual with ASD will not ever speak. Many autistic children with delayed speech later on acquire the ability to communicate through spoken language. There are various techniques used to encourage speech. These are not proven to work on every individual. However, research suggests that use of several approaches may improve verbal communication. Some of these approaches are speech therapy , behavioral interventions , play therapy and music therapy. The best way to help children with ASD build their communication skills is to begin treatment as soon as possible. Early intervention is of utmost importance for nonverbal individuals.

A child not speaking to communicate doesn’t mean that they have low IQ. Late acquisition of language does not necessarily mean poor prognosis. It is seen time and again that children with autism may develop language later compared to typically developing children. This means that parents and caregivers should not give up on speech therapy. There are many tools to aid this process. At this day and age, an abundance of digital tablets and autism applications may also help.


This article is examined by Clinical Child Psychologist and Ph. D. Researcher Kevser Çakmak, and produced by Otsimo Editorial Team.

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