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Zhu, H. Low-Functioning Autism. Encyclopedia. Available online: (accessed on 06 December 2023).
Zhu H. Low-Functioning Autism. Encyclopedia. Available at: Accessed December 06, 2023.
Zhu, Handwiki. "Low-Functioning Autism" Encyclopedia, (accessed December 06, 2023).
Zhu, H.(2022, October 25). Low-Functioning Autism. In Encyclopedia.
Zhu, Handwiki. "Low-Functioning Autism." Encyclopedia. Web. 25 October, 2022.
Low-Functioning Autism

Low-functioning autism (LFA) is autism with low functioning levels. Symptoms may include impaired social communications or interactions, bizarre behavior, and lack of social or emotional reciprocity. Sleep problems, aggressiveness, and self-injurious behavior are also possible consequences. LFA is not a recognized diagnosis in the DSM-5 or ICD-10, neither of which subdivides autism based on intellectual capabilities. Synonyms include Kanner's syndrome, Kannerian autism and classic autism. The terms overlap with severe autism and profound autism (as opposed to "mild" or "moderate"), which may be vaguely defined and not necessarily correlate with severe and profound levels of intellectual disability (where profound is the most severe level).

intellectual disability self-injurious behavior sleep

1. Characterization

Those who display symptoms for LFA usually have "impairments in all the three areas of psychopathology: reciprocal social interaction, communication, and restricted, stereotyped, repetitive behaviour".[1]

Severe impairment of social skills can be seen in people with LFA.[2] This could include a lack of eye contact,[3] inadequate body language and a lack of emotional or physical response to others' behaviors and emotions. These social impairments can cause difficulty in relationships.[4]

Communication impairments shown in people with LFA include lack of communication (both oral communication – i.e. nonverbal autism – and body language), repetitive use of words or phrases, and lack of imaginative play skills.[4] They also may respond only to very direct external social interaction from others. Specific behavioral impairments that may be exhibited by a person with LFA include adherence to nonfunctional rituals or routines, repetitive motor functions such as hand flapping or complex whole body movements, and restrictive or obsessive patterns of interest that are abnormal. Other symptoms may include preoccupation with sensory elements of play materials such as their odor, feel, or noise they generate.[5]

1.1. Behavior

An association between high-functioning autism (HFA) and criminal behavior is not completely characterized. Several studies have shown that the features associated with HFA may increase the probability of engaging in criminal behavior.[6] While there is still a great deal of research that needs to be done in this area, recent studies on the correlation between HFA and criminal actions suggest that there is a need to understand the attributes of HFA that may lead to violent behavior. There have been several case studies that link the lack of empathy and social naïveté associated with HFA to criminal actions.[7]

More research is needed on the link between HFA and crimes, because most other studies point out that most people with autism spectrum disorders are ten times more likely to be victims and five times less likely to commit crimes than the general population. But there are also small subgroups of people with LFA that commit crimes, because of a lack of understanding of the laws.

On average, people with LFA are 20 times more likely to be victims and ten times less likely to commit crimes than all populations combined. There are however rare cases of people with LFA that commit crimes, due to insanity or diminished capacity, due to the severity of lack of social skills and intellectual disabilities.

2. Causes

The exact causes of autism are unknown, but it is believed that both genetic and environmental factors play a role in its development.[8] Multiple studies have shown structural and functional abnormalities in the brains of autistic people.[4] Experiments have been conducted to determine if the degree of brain abnormality yields any correlation to the severity of autism. One study done by Elia et al. (2000) used magnetic resonance imaging (MRI) on the midsagittal area of the cerebrum, midbrain, cerebellar vermis, corpus callosum, and vermal lobules VI and VII to measure brain abnormalities in children with low-functioning autism. The results suggested that the midbrain structures correlate with certain developmental behavioral aspects such as motivation, mnemonic, and learning processes, though there is more research needed to confirm this.[9] Furthermore, many developmental processes may contribute to several types of brain abnormalities in autism; therefore, determining the link between such abnormalities and severity of autism proves difficult.[4]

3. Diagnosis

While low-functioning autism has never been an official diagnosis in the Diagnostic and Statistical Manual of Mental Disorders published by the American Psychiatric Association, it was a classification in the DSM-4 to refer to someone with autism who has an intellectual disability (an IQ of 69 or below). But in the present diagnostic standards in the DSM-5, the classification of LFA has been removed.[10]

The criteria for autism spectrum disorders in the DSM-5 is broken down into three levels of support required, the criteria for level 3 (requiring very substantial support) includes severe deficits in communication skills (verbal and nonverbal), inflexibility of behavior, extreme difficulty coping with change, and extreme difficulty with shifting focus and attention. Individuals with level 3 autism would initiate very limited amounts of social interactions and would respond only to direct social approaches from others.[5]

The ICD-10 criteria for childhood autism postulate that abnormal or impaired development is evident before the age of 3 in receptive or expressive language used in social communication, development of selective social attachments or reciprocal social interactions, or functional and symbolic play. The children would also be required to exhibit six other symptoms from three macro-categories pertaining to qualitative impairment in social interactions, quantitative abnormalities in communication, and restricted/repetitive/stereotyped patterns of behavior, interests, and activities. ICD-10 differentiates high functioning and low-functioning autistic people by diagnosing the additional code of intellectual disability.[11]

4. Therapy

4.1. Augmentative and Alternative Communication

Augmentative and alternative communication (AAC) is used for autistic people who cannot communicate orally. People who have problems speaking may be taught to use other forms of communication, such as body language, computers, interactive devices, and pictures.[12] The Picture Exchange Communication System (PECS) is a commonly used form of augmentative and alternative communication with children and adults who cannot communicate well orally. People are taught how to link pictures and symbols to their feelings, desires and observation, and may be able to link sentences together with the vocabulary that they form.[13]

4.2. Speech-Language Therapy

Speech-language therapy can help those with autism who need to develop or improve communication skills.[1] According to the organization Autism Speaks, "speech-language therapy is designed to coordinate the mechanics of speech with the meaning and social use of speech".[13] People with low-functioning autism may not be able to communicate with spoken words. Speech-language pathologists (SLP) may teach someone how to communicate more effectively with others or work on starting to develop speech patterns.[14] The SLP will create a plan that focuses on what the child needs.

4.3. Occupational Therapy

Occupational therapy helps autistic children and adults learn everyday skills that help them with daily tasks, such as personal hygiene and movement. These skills are then integrated into their home, school, and work environments. Therapists will oftentimes help people learn to adapt their environment to their skill level.[15] This type of therapy could help autistic people become more engaged in their environment.[13] An occupational therapist will create a plan based on a person's needs and desires and work with them to achieve their set goals.

4.4. Sensory Integration Therapy

Sensory integration therapy helps people with autism adapt to different kinds of sensory stimuli. Many with autism can be oversensitive to certain stimuli, such as lights or sounds, causing them to overreact. Others may not react to certain stimuli, such as someone speaking to them.[16] Many types of therapy activities involve a form of play, such as using swings, toys and trampolines to help engage people with sensory stimuli.[13] Therapists will create a plan that focuses on the type of stimulation the person needs integration with.

4.5. Applied Behavioral Analysis (ABA)

Applied behavioral analysis (ABA) is considered the most effective therapy for autism spectrum disorders by the American Academy of Pediatrics.[17] ABA focuses on teaching adaptive behaviors like social skills, play skills, or communication skills[18][19] and diminishing problematic behaviors like eloping or self-injury[20] by creating a specialized plan that uses behavioral therapy techniques such as positive or negative reinforcement to encourage or discourage certain behaviors over-time.[21]

4.6. Medication

There are no medications specifically designed to treat autism. Medication is usually used for problems as a cause of autism, such as depression, anxiety, or behavioral problems.[22] Medicines are usually used after other alternative forms of treatment have failed.[23]


  1. "What is Autism, Asperger Syndrome, and Pervasive Developmental Disorders?". Retrieved 2 September 2019. 
  2. "Autism (Autism Spectrum Disorder - ASD): Symptoms of Autism Spectrum Disorder" (in en). 29 April 2020. 
  3. "Why do those with autism avoid eye contact? Imaging studies reveal overactivation of subcortical brain structures in response to direct gaze" (in en). 
  4. Brambilla, P (2003). "Brain anatomy and development in autism: Review of structural MRI studies". Brain Research Bulletin 61 (6): 557–569. doi:10.1016/j.brainresbull.2003.06.001. PMID 14519452.
  5. "DSM-5 Diagnostic Criteria". Retrieved 16 December 2015. 
  6. Mazzone, Luigi; Ruta, Liliana; Reale, Laura (2012). "Psychiatric comorbidities in asperger syndrome and high functioning autism: Diagnostic challenges". Annals of General Psychiatry 11 (1): 16. doi:10.1186/1744-859X-11-16. PMID 22731684.
  7. Lerner, Matthew D.; Haque, Omar Sultan; Northrup, Eli C.; Lawer, Lindsay; Bursztajn, Harold J. (2012). "Emerging Perspectives on Adolescents and Young Adults With High-Functioning Autism Spectrum Disorders, Violence, and Criminal Law". Journal of the American Academy of Psychiatry and the Law 40 (2): 177–90. PMID 22635288. 
  8. "Autism Spectrum Disorder: Fact Sheet". Retrieved 16 December 2015. 
  9. Elia, M; Ferri, R; Musumeci, S; Panerai, S; Bottitta, M; Scuderi, C (2000). "Clinical Correlates of Brain Morphometric Features of Subjects With Low-Functioning Autistic Disorder". Journal of Child Neurology 15 (8): 504–508. doi:10.1177/088307380001500802. PMID 10961787.
  10. "What is Autism, Asperger Syndrome, and Pervasive Developmental Disorders?". Retrieved 16 December 2015. 
  11. Strunecká, A (2011). Cellular and molecular biology of autism spectrum disorders. Bentham e Books. pp. 4–5. 
  12. "Augmentative and Alternative Communication (AAC)". 
  13. "What Treatments are Available for Speech, Language and Motor Issues?". 
  14. "Speech and Language Therapy". 
  15. "Occupational Therapy's Role with Autism". 
  16. Smith, M; Segal, J; Hutman, T. Autism Spectrum Disorders. 
  17. Myers, Scott M.; Johnson, Chris Plauché (1 November 2007). "Management of Children With Autism Spectrum Disorders". Pediatrics 120 (5): 1162–1182. doi:10.1542/peds.2007-2362. ISSN 0031-4005. PMID 17967921. 
  18. "Applied Behavioral Analysis (ABA): What is ABA?". 
  19. Matson, Johnny; Hattier, Megan; Belva, Brian (January–March 2012). "Treating adaptive living skills of persons with autism using applied behavior analysis: A review". Research in Autism Spectrum Disorders 6 (1): 271–276. doi:10.1016/j.rasd.2011.05.008.
  20. Summers, Jane; Sharami, Ali; Cali, Stefanie; D'Mello, Chantelle; Kako, Milena; Palikucin-Reljin, Andjelka; Savage, Melissa; Shaw, Olivia et al. (November 2017). "Self-Injury in Autism Spectrum Disorder and Intellectual Disability: Exploring the Role of Reactivity to Pain and Sensory Input". Brain Sci 7 (11): 140. doi:10.3390/brainsci7110140. PMID 29072583.
  21. "Applied Behavioral Strategies - Getting to Know ABA". 
  22. National Institute of Mental Health. "Medications for Autism". 
  23. Pope, J; Volkmar, F (November 14, 2014). Medicines for Autism. 
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