Typically, the symptoms of ASD are recognized between 12 and 24 months of age. They may be seen earlier than 12 months if a child’s developmental delays are severe, or not seen until after 24 months if a child’s symptoms are more subtle. The symptoms of ASD impact children in two meaningful ways:

  • These children experience challenges with communicating and socializing with others
  • These children have repetitive and restricted behaviors and/or interests.

Our understanding of ASD has changed over time. In the past, children were diagnosed with one of several different conditions known as pervasive developmental disorders (PDDs):

  • Autism
  • Asperger’s Disorder
  • Childhood Disintegrative Disorder (CDD)
  • Pervasive Developmental Disorder Not Otherwise Specified (PDD-NOS)

Now, all of these are considered ASD. Because children with ASD can have a range of different symptoms and behaviors, it is considered a “spectrum disorder”. The term “spectrum” refers to the many different autistic characteristics–and combinations of characteristics–that can exist in several functional domains. These areas include social communication, social awareness, sensory processing, information processing, repetitive behaviors, and cognitive thinking style.

What are the symptoms of ASD?

ASD looks different in each child, and not every child shows every symptom. For some children, the symptoms are mild, and for others the symptoms are severe. Children with ASD often show symptoms by the time they reach 2 years of age, although there are some children whose symptoms remain unproblematic or unnoticed until they are older. Some children even begin to lose or “regress” in their language, motor, or social skills between 1 and 2 years of age.

Symptoms of ASD are grouped into two categories: deficits in social communication and social interaction; and restricted and repetitive behaviors and interests. The symptoms must be present early in the child’s life even if they do not result in challenges until later in life (i.e., after increasingly complex social interactions begin to surpass the child’s capacities), and they must result in significant impairment in other aspects of everyday life (e.g., social, familial, academic, etc.).

Deficits in social communication and social interaction

Restricted and repetitive behaviors and interests

  • Difficulties understanding other childrens’ or adults’ emotions and perspective
  • Difficulties with understanding and using nonverbal communication
  • Difficulties making and maintaining social relationships
  • Repetitive or “stereotyped” motor movements, speech, or use of objects (e.g., finger movements, hands flapping, rocking back and forth, etc.)
  • Ritualized patterns of behavior (e.g., strictly doing the same activity always at the same time)
  • Highly restricted or fixated interests
  • Sensory hypo- or hyper-reactivity (e.g., expressing extreme discomfort in loud, crowded or bright places)

Associated symptoms of ASD

  • Delays in learning to speak
  • Rarely or poorly making eye contact with others
  • Expressing cuddling or hugging dislike
  • Preferring solo play or having trouble playing along with others
  • Having trouble using motions or gestures to communicate
  • Sounding like a robot when speaking or speaking in a sing-song way
  • Repeating phrases over and over
  • Trouble with participating in a conversation
  • Trouble making friends
  • Repeating the same action over and over again
  • Struggling when changes to a routine are needed
  • Putting toys in order instead of playing with them
  • Becoming extremely focused on objects or topics

Neurodiversity refers to the differences in the way people’s brains work–that there is no “correct” way for the brain to work. Instead, there is a wide range of ways that kids perceive and respond to the world around them and, while these differences may result in symptoms or impairments, they can also be embraced and encouraged. Support and treatment can also help reduce symptoms that interfere with kids achieving their goals.

How is ASD diagnosed?

The diversity of ASD can make it difficult to correctly diagnose it. Sometimes children with ASD are mistakenly diagnosed with a different disorder, like Attention-Deficit/Hyperactivity Disorder (ADHD) or Oppositional Defiant Disorder (ODD), or they are told that nothing is wrong. Other times kids are diagnosed with ASD when they do not properly meet the criteria.

To be diagnosed with ASD, a child must have symptoms that include both social challenges and repetitive behaviors. These symptoms must get in the way of the child’s daily life. Symptoms must exist or be tracked down by the time the child is two years old, even if they are not obvious until the child is older. Autism can be diagnosed in kids as young as 2 years old. There are three severity levels for ASD (see table below).

Severity Levels for ASD

Social Communication

Restricted, Repetitive Behaviors

Level 1 “Requiring Support”

Social communication difficulties will be noticeable ​​without support. These may include issues with initiating interactions, responding to peer attempts to initiate, or even showing a lack of interest in interacting. Attempts to make friends may seem rather odd or may be unsuccessful.

Rigid or inflexible thinking or behavior causes difficulties, such as with making transitions or switching between activities, in more than one setting. With older children and adolescence, difficulties with organizing and making plans reduce independence.

Level 2 “Requiring Substantial Support”

Even with support, there are marked difficulties with verbal communication, nonverbal communication, and socialization. These include poor attempts to interact, interacting only when a topic of interest is involved, odd communication, or a lack of interest in interacting with peers and caregivers beyond having needs met.

Rigid or inflexible thinking or behavior cause notable difficulties, such as being unable to cope with changes or transitions or experiencing distress when others do not adhere to the child’s rigid demands. Restricted/repetitive behaviors are present and are often obvious to non-caregivers.

Level 3 “Requiring Very Substantial Support”

Even with support, verbal and nonverbal social communications are very limited and prevent the child from successfully engaging in social interactions. The child is unlikely to initiate interactions with others or respond to others’ attempts to interact.

Very severe rigid or inflexible thinking or behavior, as well as restricted/repetitive behaviors interfere with the child’s ability to function. The child experiences great distress when changes or transitions occur.

ASD is diagnosed by child psychiatrists and the most common sources of referrals are parents, pediatricians, and nursery schoolteachers. Evaluations include assessment of the child’s behaviors in different settings and within the context of their overall development, and it should incorporate both clinician observations and parent/caregiver interviews. Additionally, comprehensive evaluations will include information about other areas of a child’s functioning across contexts. Assessing a child’s cognitive, motor, language and adaptive functioning can provide information on the most appropriate treatments and the impact their symptoms are having on their overall functioning.

Specific questionnaires may be used before a formal screening (e.g., M-CHAT) by a child psychiatrist. In addition, specific interviews and observation tests (e.g., ADOS-2, ADI-R) are used in order to evaluate the strengths and weaknesses of the child so that a personalized intervention can be designed.

ASD Facts

Worldwide frequency of the condition

The percentage of the world’s school-aged children and adolescents with ASD varies from study to study, ranging from 1% to 2%. A recent review of European students, estimated ASD prevalence to be 1.4%.

Burden of the condition in Greece

ASD accounts for 2% for all disability adjusted life years (DALYs) lost to health conditions in Greece for 5- to 14-year-old children and adolescents. It is the 4th most prominent mental health condition adding to the health burden of the Greek child and adolescent population.

Gender ratio

While the male-female comparative data for ASD is often assumed to be 4:1, a recent systematic review and meta-analysis shows the ratio is closer to 3:1, with the difference resulting from gender bias.

Peak age of onset

The peak age of onset for ASD is estimated to be 5.5 years.

Proportion of the condition that emerges before age 18

According to recent data, 89.8% of individuals with ASD will have been diagnosed by the time they are 18 years old.

What are the associated factors for ASD?

Some common factors associated with ASD are:

  • Genetic and familial factors. There is an increased risk for children with an older sibling with ASD. Additional familial factors include maternal age higher than ≥35 years and paternal age higher than >45 years, as well as maternal obesity or hypertension.
  • Complications during pregnancy. These include gestational diabetes melitus; exposure to a medication called valproate during pregnancy.
  • Fewer than 12 months between pregnancies.
  • Preterm birth.
  • Complications during childbirth, such as neonatal hypoxia.

Studies have since shown that there is no link between vaccines and autism. Folic acid intake during pregnancy has been shown to be a protective factor for ASD.

What other disorders co-occur with ASD?

Even though each child is different, ASD might commonly co-occur with Intellectual Disability and Language Disorder. Many children with ASD might have symptoms that indicate multiple other mental health disorders. When a child with ASD meets the criteria for another disorder, including ADHD, Developmental Coordination Disorder, anxiety disorders, or mood disorders, each applicable diagnosis should be added to the child’s profile.

Epilepsy is common in people with autism, especially those with Intellectual Developmental Disorder, and usually first appears in early adolescence.

How is ASD Treated?

Behavioral and psychosocial treatments have been shown to benefit some children and adolescents with ASD in some areas of functioning, such as cognition and adaptive functioning. Intervening early is a priority not only because it might increase the chances of the child communicating and interacting better with others, but produce some structure to parents, who usually find the child's behavior challenging to manage and require intensive support from professionals. Various interventions are currently available, and can help families at different levels, as described below:

  • Preventing or minimizing the deterioration of associated symptoms. Following medical recommendations on regular screening and management of comorbid medical conditions, can help lessen several mental health implications. Early intervention is a term used to describe a package of diagnostic and therapeutic services provided to children and families with developmental disorders, earlier than 3 years of age. Beginning services early can have exponentially more impactful results in learning, behavior and function.
  • Limiting the extent of impairment in a child’s daily life. Specialized multidisciplinary services include occupational therapy, physical therapy, speech-language therapy, family counseling. Individual, family, and group behavioral and cognitive-behavioral psychotherapy can help to improve daily life skills, as well as cognitive and social skills.
  • Supporting the way a child can function better and improve their overall quality of life. These interventions aim to support children and adolescents with ASD in their individualized educational needs, to engage them in socializing and vocational rehabilitation programs, and to prepare them for appropriate integration to the community on their journey into adulthood. Adults with mild and some with moderate ASD may lead independent lives.

There is no medication for the symptoms of ASD. But children on the spectrum may take medication that is aimed at curbing aggression or other impairing behaviors. Kids on the autism spectrum may also take medication for other disorders that they may have, including anxiety, depression or ADHD. Even though this is particularly important for children who may have multiple diagnoses, any medical professional prescribing medication should do so carefully.

Where to find more information

If you need more information on social communication, restricted and repetitive behaviors and interests, and reasons for concerns, you can also go to "Difficulties with social communication" and "Restricted and repetitive behaviors and interests" on our website.

To learn more about the technical work conducted to develop this guide, please consult our reference list here:

References

Clinical description, symptoms, and diagnostic information

  • American Psychiatric Association. (2022). Diagnostic and Statistical Manual of Mental Disorders: Fifth Edition Text Revision DSM-5-TR. American Psychiatric Association Publishing, Washington, DC.
  • Child Mind Institute. (2022, March 29). Complete Guide to Autism. https://childmind.org/guide/parents-guide-to-autism/
  • Lord, C., Brugha, T. S., Charman, T., Cusack, J., Dumas, G., Frazier, T., Jones, E. J. H., Jones, R. M., Pickles, A., State, M. W., Taylor, J. L., & Veenstra-VanderWeele, J. (2020). Autism spectrum disorder. Nature Reviews Disease Primers, 6(1), 5. https://doi.org/10.1038/s41572-019-0138-4
  • World Health Organization. (2022, February). ICD-11 for Mortality and Morbidity Statistics. 6A02 Autism Spectrum Disorder. https://icd.who.int/browse11/l-m/en#/http://id.who.int/icd/entity/437815624

Facts

  • American Psychiatric Association. (2022). Diagnostic and Statistical Manual of Mental Disorders: Fifth Edition Text Revision DSM-5-TR. American Psychiatric Association Publishing, Washington, DC
  • Arango, C., Dragioti, E., Solmi, M., Cortese, S., Domschke, K., Murray, R. M., Jones, P. B., Uher, R., Carvalho, A. F., Reichenberg, A., Shin, J. I., Andreassen, O. A., Correll, C. U., & Fusar‐Poli, P. (2021). Risk and protective factors for mental disorders beyond genetics: An evidence‐based atlas. World Psychiatry, 20(3), 417–436. https://doi.org/10.1002/wps.20894
  • Institute for Health Metrics and Evaluation (IHME). (2019). GBD Compare Data Visualization. Seattle, WA: IHME, University of Washington, Available from http:// vizhub.healthdata.org/gbd-compare. (Accessed 11/15/2022)
  • Kendler, K. S. (2013). What psychiatric genetics has taught us about the nature of psychiatric illness and what is left to learn. Molecular Psychiatry, 18(10), 1058–1066. https://doi.org/10.1038/mp.2013.50
  • Loomes, R., Hull, L., & Mandy, W. P. L. (2017). What is the male-to-female ratio in Autism Spectrum Disorder? A systematic review and meta-analysis. Journal of the American Academy of Child & Adolescent Psychiatry, 56(6), 466–474. https://doi.org/10.1016/j.jaac.2017.03.013
  • Polyak, A., Rosenfeld, J. A., & Girirajan, S. (2015). An assessment of sex bias in neurodevelopmental disorders. Genome Medicine, 7(1), 94. https://doi.org/10.1186/s13073-015-0216-5
  • Sacco, R., Camilleri, N., Eberhardt, J., Umla-Runge, K., & Newbury-Birch, D. (2022). A systematic review and meta-analysis on the prevalence of mental disorders among children and adolescents in Europe. European Child & Adolescent Psychiatry. https://doi.org/10.1007/s00787-022-02131-2
  • Solmi, M., Radua, J., Olivola, M., Croce, E., Soardo, L., Salazar de Pablo, G., Il Shin, J., Kirkbride, J. B., Jones, P., Kim, J. H., Kim, J. Y., Carvalho, A. F., Seeman, M. V., Correll, C. U., & Fusar-Poli, P. (2022). Age at onset of mental disorders worldwide: Large-scale meta-analysis of 192 epidemiological studies. Molecular Psychiatry, 27(1), 281–295. https://doi.org/10.1038/s41380-021-01161-7

Associated factors

  • American Psychiatric Association. (2022). Diagnostic and Statistical Manual of Mental Disorders: Fifth Edition Text Revision DSM-5-TR. American Psychiatric Association Publishing, Washington, DC
  • Arango, C., Dragioti, E., Solmi, M., Cortese, S., Domschke, K., Murray, R. M., Jones, P. B., Uher, R., Carvalho, A. F., Reichenberg, A., Shin, J. I., Andreassen, O. A., Correll, C. U., & Fusar‐Poli, P. (2021). Risk and protective factors for mental disorders beyond genetics: An evidence‐based atlas. World Psychiatry, 20(3), 417–436. https://doi.org/10.1002/wps.20894
  • Ghirardi, L., Kuja‐Halkola, R., Butwicka, A., Martin, J., Larsson, H., D’Onofrio, B. M., Lichtenstein, P., & Taylor, M. J. (2021). Familial and genetic associations between autism spectrum disorder and other neurodevelopmental and psychiatric disorders. Journal of Child Psychology and Psychiatry, 62(11), 1274–1284. https://doi.org/10.1111/jcpp.13508
  • Hultman, C. M., Sandin, S., Levine, S. Z., Lichtenstein, P., & Reichenberg, A. (2011). Advancing paternal age and risk of autism: New evidence from a population-based study and a meta-analysis of epidemiological studies. Molecular Psychiatry, 16(12), 1203–1212. https://doi.org/10.1038/mp.2010.121
  • Kendler, K. S. (2013). What psychiatric genetics has taught us about the nature of psychiatric illness and what is left to learn. Molecular Psychiatry, 18(10), 1058–1066. https://doi.org/10.1038/mp.2013.50
  • Qiu, S., Qiu, Y., Li, Y., & Cong, X. (2022). Genetics of autism spectrum disorder: An umbrella review of systematic reviews and meta-analyses. Translational Psychiatry, 12(1), 249. https://doi.org/10.1038/s41398-022-02009-6
  • Robinson, E. B., Samocha, K. E., Kosmicki, J. A., McGrath, L., Neale, B. M., Perlis, R. H., & Daly, M. J. (2014). Autism spectrum disorder severity reflects the average contribution of de novo and familial influences. Proceedings of the National Academy of Sciences, 111(42), 15161–15165. https://doi.org/10.1073/pnas.1409204111

Co-occurring disorders

  • American Psychiatric Association. (2022). Diagnostic and Statistical Manual of Mental Disorders: Fifth Edition Text Revision DSM-5-TR. American Psychiatric Association Publishing, Washington, DC
  • Muskens, J. B., Velders, F. P., & Staal, W. G. (2017). Medical comorbidities in children and adolescents with autism spectrum disorders and attention deficit hyperactivity disorders: A systematic review. European Child & Adolescent Psychiatry, 26(9), 1093–1103. https://doi.org/10.1007/s00787-017-1020-0
  • Mutluer, T., Aslan Genç, H., Özcan Morey, A., Yapici Eser, H., Ertinmaz, B., Can, M., & Munir, K. (2022). Population-Based Psychiatric Comorbidity in Children and Adolescents With Autism Spectrum Disorder: A Meta-Analysis. Frontiers in Psychiatry, 13, 856208. https://doi.org/10.3389/fpsyt.2022.856208
  • Strasser, L., Downes, M., Kung, J., Cross, J. H., & De Haan, M. (2018). Prevalence and risk factors for autism spectrum disorder in epilepsy: A systematic review and meta-analysis. Developmental Medicine & Child Neurology, 60(1), 19–29. https://doi.org/10.1111/dmcn.13598
  • van Steensel, F. J. A., Bögels, S. M., & Perrin, S. (2011). Anxiety Disorders in Children and Adolescents with Autistic Spectrum Disorders: A Meta-Analysis. Clinical Child and Family Psychology Review, 14(3), 302–317. https://doi.org/10.1007/s10567-011-0097-0

Interventions

  • Correll CU, Cortese S, Croatto G, et al. Efficacy and acceptability of pharmacological, psychosocial, and brain stimulation interventions in children and adolescents with mental disorders: an umbrella review. World Psychiatry. 2021;20(2):244-275. doi:10.1002/wps.20881
  • Hampton, L. H., & Kaiser, A. P. (2016). Intervention effects on spoken-language outcomes for children with autism: A systematic review and meta-analysis: Spoken-language outcomes for children with autism. Journal of Intellectual Disability Research, 60(5), 444–463. https://doi.org/10.1111/jir.12283
  • Kulasinghe, K., Whittingham, K., Mitchell, A. E., & Boyd, R. N. (2022). Psychological interventions targeting mental health and the mother–child relationship in autism: Systematic review and meta‐analysis. Developmental Medicine & Child Neurology, dmcn.15432. https://doi.org/10.1111/dmcn.15432
  • Lord C, Brugha TS, Charman T, et al. Autism spectrum disorder. Nat Rev Dis Primers. 2020;6(1):5. doi:10.1038/s41572-019-0138-4
  • Murza, K. A., Schwartz, J. B., Hahs-Vaughn, D. L., & Nye, C. (2016). Joint attention interventions for children with autism spectrum disorder: A systematic review and meta-analysis: Joint attention meta-analysis. International Journal of Language & Communication Disorders, 51(3), 236–251. https://doi.org/10.1111/1460-6984.12212
  • Nahmias, A. S., Pellecchia, M., Stahmer, A. C., & Mandell, D. S. (2019). Effectiveness of community‐based early intervention for children with autism spectrum disorder: A meta‐analysis. Journal of Child Psychology and Psychiatry, 60(11), 1200–1209. https://doi.org/10.1111/jcpp.13073
  • Siafis, S., Çıray, O., Wu, H., Schneider-Thoma, J., Bighelli, I., Krause, M., Rodolico, A., Ceraso, A., Deste, G., Huhn, M., Fraguas, D., San José Cáceres, A., Mavridis, D., Charman, T., Murphy, D. G., Parellada, M., Arango, C., & Leucht, S. (2022). Pharmacological and dietary-supplement treatments for autism spectrum disorder: A systematic review and network meta-analysis. Molecular Autism, 13(1), 10. https://doi.org/10.1186/s13229-022-00488-4
  • Tachibana, Y., Miyazaki, C., Ota, E., Mori, R., Hwang, Y., Kobayashi, E., Terasaka, A., Tang, J., & Kamio, Y. (2017). A systematic review and meta-analysis of comprehensive interventions for pre-school children with autism spectrum disorder (ASD). PLOS ONE, 12(12), e0186502. https://doi.org/10.1371/journal.pone.0186502
  • Tarver, J., Palmer, M., Webb, S., Scott, S., Slonims, V., Simonoff, E., & Charman, T. (2019). Child and parent outcomes following parent interventions for child emotional and behavioral problems in autism spectrum disorders: A systematic review and meta-analysis. Autism, 23(7), 1630–1644. https://doi.org/10.1177/1362361319830042
  • Ung, D., Selles, R., Small, B. J., & Storch, E. A. (2015). A Systematic Review and Meta-Analysis of Cognitive-Behavioral Therapy for Anxiety in Youth with High-Functioning Autism Spectrum Disorders. Child Psychiatry & Human Development, 46(4), 533–547. https://doi.org/10.1007/s10578-014-0494-y
  • Wichers, R. H., van der Wouw, L. C., Brouwer, M. E., Lok, A., & Bockting, C. L. H. (2023). Psychotherapy for co-occurring symptoms of depression, anxiety and obsessive-compulsive disorder in children and adults with autism spectrum disorder: A systematic review and meta-analysis. Psychological Medicine, 53(1), 17–33. https://doi.org/10.1017/S0033291722003415

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