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Severe Low Functioning Autism – What Sets it Apart

November 21, 2023

What makes severe autism so challenging? Individuals diagnosed with Level 3 autism need more support than their peers. Their symptoms are more pronounced and affect daily functioning to a great extent. Challenges include social difficulties, trouble with verbal and nonverbal communication, and rigid behavior. Treatments for severe autism are available and are most effective when implemented early.


What is low functioning autism?

The difference between high functioning autism and low functioning autism is behavioral. Low functioning autism causes behaviors that inhibit the ability to conduct daily life. Children with high functioning autism have similar abilities to his/her neurotypical peers.

This is especially true when the child receives early intervention therapies. Children diagnosed with low functioning autism need more support. They struggle to communicate and manage their behaviors.

Symptoms are identifiable in infancy or early childhood. Children with autism spectrum disorder (ASD) will not meet neurodevelopmental benchmarks on time or at all. These children experience delays in learning how to self-soothe, forming bonds, and talking. They usually experience severe communication and behavioral challenges.

Children with low functioning autism struggle to complete activities of daily living. They generally need help with most activities. Children with severe autism are more likely to have co-morbid conditions. These include such as Fragile X syndrome, tuberous sclerosis, and epilepsy.

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Low Functioning Autism

Ways low functioning autism differs from high-functioning autism

No two children with ASD will experience the same symptoms. Rather, doctors place children on a spectrum according to severity.

Asperger’s syndrome is now considered “related to by distinct from autism.” Children with Asperger’s syndrome are the highest functioning on the spectrum. Children with limited communication skills and behavioral regulation have low functioning autism.

The Three Levels of Autism

The Diagnostic and Statistical Manual of Mental Disorders (DSM-5) categorizes autism into levels. Level one is the highest functioning category. Children with Level 1 autism need support but can learn a variety of social skills. They are usually able to gain some independence. Individuals diagnosed with Level 2 autism have verbal, social, and behavioral deficits. Even with supports in place, they might struggle with these behaviors. Level 3 autism is the most severe and lowest functioning category. Those with Level 3 autism have immense difficulty socializing, speaking, and communicating nonverbally. These children experience great distress in situations outside of his/her comfort zone.

Signs of severe autism

Doctors can identify the signs of low functioning autism as early as infancy. Even more noticeable symptoms presented by preschool age. Research scientists at the Mayo Clinic, NINDS, and Nemours list the following as signs:

Impaired Social Interaction

Social interactions for children with severe autism ranges from difficult to near impossible. Some children will hit milestones and then experience regression. Skills acquired between the age of three to five experience the most regression. Other children will never develop the skills.

Children with autism are often mislabeled as lacking empathy. Their limited emotional range and poor emotional intelligence can make relating difficult. It is rare that a child with autism has no empathy. Expressing empathy can be challenging though.

Inappropriate responses are hallmark signs of low functioning autism. A child with Level 3 autism might laugh when a peer is in pain or display a lack of engagement. Most children will display a lack of social responsiveness. This might present as limited eye-contact, no acknowledgment of others’, and rare smiling. Children with autism generally have a hard time comprehending facial expressions. Poor nonverbal communication skills are more pronounced in low functioning children. Their faces often remain blank even as they are experiencing pain.

Socializing with children can be particularly difficult for those with low functioning autism. An imaginative play might be boring, and many children struggle to maintain game rules. Others find engaging in group play impossible or uninteresting. Initiating conversations can be difficult and maintaining them even is even harder. Some children communicate in social settings by using single words or short phrases. Labeling items can be helpful.

Change, whether it be in a regression. or the home routine, can be difficult for children with low functioning autism. They may become uncooperative, resistant, passive, aggressive, or disruptive. These reactions can make friendships hard to establish and maintain. Parallel play is an alternative for children who are not overwhelmed by their peers.

Communication Difficulties

Difficulty communicating is one of the first indicators that a child has autism. In infancy, autistic children may not babble or point. By age two, they may not be speaking short phrases. It is common for children who struggle to communicate to have frequent tantrums.

The inability to communicate hunger, pain, or preferences, is isolating and frustrating. Children with limited communication skills might not respond to their names. Parents or caregivers often go ignored. The child may appear to function in two modes: aloof and enraged.

By age four, a child with low functioning autism may remain nonverbal. They might continue to experience speech delays or experience speech regression. Verbal children may speak with an abnormal tone or rhythm such as singsong or monotone. The child may develop language skills and repeat phrases verbatim.

Usually, this occurs without the ability to contextualize what he/she are saying. For example, idioms are a favorite to repeat. A child might say “You’re the apple of my eye,” over and over with little to no understanding of what the phrase means. They may also take idioms literally. A cliché such as “It’s raining cats and dogs,” could evoke fear or immense confusion.

Low functioning autistic children may also mimic body language and tone without comprehension. Other children might struggle with literal speech and directions. Building a vocabulary can be a very difficult skill. No matter an autistic child’s verbal abilities, very few enjoy small talk. Children with lower functioning autism might find it impossible, while it annoys others. Speaking concisely is the best way to speak to a verbal child with low functioning autism.

Obsessive-Compulsive Disorder, Anxiety, and Behavior

Children with low functioning autism often exhibit symptoms associated with obsessive-compulsive disorder. Sensory overload or deprivation are common triggers for obsessions and compulsions. A child with autism plays in ways that neurotypical individuals may find abnormal. Children with autism might prefer categorizing or lining up toys to creating narratives.

The child may exhibit an intense fixation on activity to the point of obsession. This might inhibit him/her from contextualizing his/her toys. A child with autism might find details fascinating, but struggle to understand function. For example, the spinning wheels on a toy car might hold a child’s attention for hours. The same child would likely ignore the function of the wheels to help the car move.

The child may also use toys in ways they were not intended. He/she might find more enjoyment turning the switch on an electronic toy on and off than playing with the toy. This behavior generally continues into primary school. The child’s neurotypical peers might be able to contextualize their toys by the age of four.

Impulse control is a struggle for many children with low functioning autism. They often fidget and find it difficult to sit still. This can take the form of repetitive kinesthetic activities, stimming, or repetitive speech. Children might also engage in self-injurious behaviors such as skin-picking, pinching, or head-banging.

They often find comfort in specific routines or rituals. Inevitable schedule changes or disruptions can be devastating. Parents often notice an exaggeration of existing troublesome behavior during these times. The child might also experience a regression or lack of impulse control.

Some children display behaviors like hitting or spitting, even in low-stress environments. These children may display an inability to understand why the behavior is undesirable. They may be unwilling to correct their behaviors or manage their impulsivities. It is uncommon for them to seek their caregivers’ approval.

 Sensory Processing Difficulties

Many parents notice sensory processing difficulties as early as their child’s infancy. Children with low functioning autism find physical touch distressing. Even touch most children find comforting, such and cuddling or handholding, is uncomfortable.

You might notice your child’s movements are clumsy, stiff, or exaggerated. This is common in children with autism even after their peers have refined motor skills. Children with sensory processing difficulties struggle to acclimate to their bodies. This is due to a hyper-awareness of movement and sensation.

The transition from walking in humid air to crisp air, or from carpet to hard floors, can be overwhelming. These children may experience a profound awareness of their senses. Touch and visual stimuli can be particularly distressing. Despite their extreme sensitivity, many children remain oblivious to self-inflicted pain.

Often, triggering stimuli can change overnight. Constant changes in food and clothing preference are common. These evolving sensitivities may trigger an angry or frustrated response.

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When should I have my child screened for autism?

If you notice two or more of these signs in your child, it is time to have him/her screened. Not meeting typical developmental benchmarks is also an indicator to screen. A multi-disciplinary team will help you with a diagnosis for your child. The process starts with a questionnaire to determine how your child functions. It will ask about your child’s behavior at home, school, and social settings. The evaluation might ask for your child’s pediatrician and teacher’s input.

If the pediatrician suspects ASD, your child will meet with a team to further test him/her. This team is usually comprised of a psychologist/psychiatrist, neurologist, and speech therapist. An audiologist might administer a hearing test to rule out auditory processing disorders.

Doctors diagnose low functioning autism on three major criteria:

  • First is your child’s ability to communicate. Your child’s doctor will assess his/her verbal skills and nonverbal communication.
  • Next, the team will observe your child’s behavior. They will watch for stimming and self-injurious behaviors. The team will pay attention to how restrictive and repetitive the behaviors are.
  • Finally, they consider the daily impact of behaviors and communication difficulties.

What are the most common comorbid conditions with severe autism?

Several institutions are researching the physical issues associated with low functioning autism. Fragile X syndrome, tuberous sclerosis, and epilepsy are the most common co-morbid diagnoses.

Fragile X Syndrome

Fragile X syndrome is a genetic condition that affects development. It is often associated with learning disabilities. Common symptoms include speech and language delays, anxiety, hyperactivity, and low impulse control. The National Institute of Health (NIH) reports that more males have Fragile X syndrome. One-third of those diagnosed will also receive an autism spectrum disorder diagnosis.

The NIH reports that most males will exhibit associated physical features. This is in relation to only half of the females with Fragile X syndrome. The most common features are long, narrow faces, large ears, and a prominent jaw and forehead. Flat feet and hyper-flexible fingers are quite common as well. Men often experience macroorchidism after puberty.

The National Human Genome Research Institute recommends seeking special education and early intervention. Anticipatory management is key. There are no current specific medications shown to help. Your pediatrician might recommend medication to control behavioral issues though. Also be aware of possible vision, hearing, connective tissue, and heart problems. Your child’s pediatrician can refer you to specialists as needed.

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Low Functioning Autism

Tuberous Sclerosis

Tuberous sclerosis (TS) is a rare genetic condition that causes benign tumors. Most often tumors appear on organs including the skin, brain, heart, eyes, kidneys, and lungs. In 2012, Xin Guo, MD, Wen-Jun Tu, MD, and Xiao-Dong Shi, MD, conducted a study to examine the rate of TS in individuals with ASD.

Over four years, they studied autistic children at the China Rehabilitation Research Center. They discovered that one in five (1.17 percent) of the 429 children involved in the study had TS. They concluded that children with low functioning autism were more likely to have TS.

The Mayo Clinic reports no current cure for TS. They list antiepileptic drugs as a possible way to control symptoms.


Epilepsy is a neurological condition that causes electrical communication disruptions between neurons. The result of this disruption is seizure activity. A seizure often looks like muscle stiffness, twitching of limbs, or a distant stare. Before or after seizure activity, severe headaches and confusion are common.

In 2011, Patrick F. Bolton, Ph.D., FRCPsych, (et al.) completed a long-term study to assess the co-occurrence of epilepsy and ASD. The researchers studied 150 children with autism until they turned 21. They found that 22% of participants developed seizure activity after turning 10.

They also found that over half of their subjects’ had seizures weekly or less. Medication helped control their symptoms. Female participants were more likely to develop seizure activity. Females with lower functioning autism and weaker verbal skills had the most seizures.

Johns Hopkins urges parents to call 911 if they think their child is experiencing a seizure. You should follow up with their pediatrician to discuss medication options. Dietary therapy, vagus nerve stimulation, and surgery are all possible treatments to consider.

Explaining autism to your family and friends

After receiving your child’s autism diagnosis, you’ll likely have new questions every day. One thing that most parents struggle with at first is how to explain autism to their friends and family. Being honest about your child’s diagnosis and how it affects him/her is important. The more you educate people in your child’s life, the more successful interactions will be.

Give people concrete ideas on how to support your child and interact with him/her. Explain to family and friends how autism affects your child. Give specific examples and explain your child’s reactions. To the extent that you are comfortable, provide comprehensive answers to their questions.

People will likely have lots of questions. It is okay to tell people you are still figuring things out. It is fine to say that you do not have all the answers and refer them to a helpful article. These conversations are ongoing ones. Each time you start a new conversation, it will likely get easier.

Ways to improve your life with a severe autism diagnosis

Children with low functioning autism have many treatment options to improve their lives. Professional support, in-home modifications, educational opportunities, and community support can be beneficial.

Professional Support

Upon receiving a diagnosis, you will need to choose a treatment team for your child. This team usually includes a pediatrician, occupational therapist, speech therapist, and psychologist. You might also include a psychiatrist to prescribe medication as needed. Autism behavioral therapists can help your child with interpersonal relationships and social skills. Depending on your child’s interests you might also choose to include an art or music therapist.

In-Home Modifications

Children with low functioning autism often struggle with impulse control. Many also have a hard time processing dangerous situations. Minimizing risk is one of the most important things you can do for your child. Locking up hazardous materials, medicine, and cleaning products is a great starting place. Some parents also opt to unplug appliances like stoves and blenders.

If your child engages in head-banging, be sure to add padding to surfaces he/she uses for self-injury. Try creating a secure space in your home where your child has free range to play and explore. This space might include a yoga ball chair, weighted blanket, and favorite toys. Your child’s pediatrician/occupational therapist can help you identify hazards.

Educational Opportunities

Children with low functioning autism deserve exceptional education. Some parents send their children to specialized schools for autism education. Other families prefer accommodations in traditional schools. Individualized Education Plans (IEPs) are necessary for most public schools. IEPs outline your child’s strengths and struggle to ensure the school meets his/her needs. An educational psychiatrist will draft the IEP with your child’s treatment team.

The psychiatrist will meet with you and ask for your input. Then they will form a plan that supports your child’s goals. Many schools offer support staff or paraprofessionals to assist students throughout the day. Your child’s IEP might specify speech therapy, occupational therapy, or recreational therapy. Some schools even staff a psychologist and psychiatrist.

Community Support

support groups for parents are available through most major hospitals. Groups are often led by a therapist, medical student, or another parent. These groups are a safe place to voice frustrations and celebrate successes.  Some hospitals also offer specialized short-term groups to teach parents practical skills. These skills empower parents to help their child lead a safe and happy life.

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