Autism Spectrum Disorder (ASD) is a neurodevelopmental disorder characterised by challenges in social communication and repetitive behaviours. The term “spectrum” reflects the wide variation in challenges and strengths possessed by each person with ASD. While there isn’t a single type of ASD, the disorder is often classified based on its severity and the presence of additional features. Here are some terms commonly used to describe different types or levels of ASD:

Autistic Disorder (Classic Autism)

Autistic Disorder, often referred to as Classic Autism, is a pervasive developmental disorder characterised by a range of impairments in social interaction, communication, and behaviour. This neurodevelopmental condition typically manifests in early childhood, with symptoms becoming evident before the age of three. One of the hallmark features of Autistic Disorder is significant challenges in social interaction and communication skills. Individuals with Classic Autism may struggle with making eye contact, understanding nonverbal cues, and engaging in reciprocal conversations. Speech and language development may also be delayed or impaired, leading to difficulties in expressing needs and forming relationships with others.

In addition to social and communication deficits, individuals with Autistic Disorder often display repetitive and stereotyped behaviours. These behaviours can include repetitive movements (such as hand-flapping or rocking), insistence on routines and rituals, and a strong preference for sameness. Sensory sensitivities are also common, with heightened or diminished responses to sensory stimuli like lights, sounds, or textures. The severity of symptoms can vary widely among individuals with Autistic Disorder, ranging from mild to severe. Early intervention and tailored support can significantly improve outcomes for individuals with Classic Autism, helping them develop essential skills and navigate the challenges associated with the condition.

Asperger’s Syndrome

Asperger’s Syndrome is a subtype of Autism Spectrum Disorder (ASD) that is characterised by specific patterns of behaviour and differences in social interaction and communication. Unlike Classic Autism, individuals with Asperger’s Syndrome typically exhibit normal to above-average intelligence and do not experience significant delays in language development. The primary challenges in Asperger’s Syndrome are related to social difficulties, restricted interests, and repetitive behaviours.

One distinguishing feature of Asperger’s Syndrome is a marked impairment in social interaction. Individuals with Asperger’s may struggle with understanding social cues, making and maintaining friendships, and engaging in reciprocal conversations. They often have difficulty grasping the unspoken rules of social interaction and may appear socially awkward or isolated. Communication patterns in Asperger’s Syndrome may be characterised by a formal or pedantic style of speech, and individuals may tend to focus intensely on specific topics of interest, sometimes to the exclusion of other subjects.

Repetitive behaviours and a preference for routines are also common in Asperger’s Syndrome, similar to other forms of ASD. However, these behaviours may be less severe compared to Classic Autism. Individuals with Asperger’s may develop intense interests in specific topics and demonstrate a deep knowledge in those areas. With appropriate support, individuals with Asperger’s Syndrome can learn strategies to navigate social situations and develop coping mechanisms to address challenges, allowing them to lead fulfilling and productive lives.

autism diagnosis

Pervasive Developmental Disorder-Not Otherwise Specified (PDD-NOS)

Pervasive Developmental Disorder-Not Otherwise Specified (PDD-NOS) was a diagnostic category that was part of the autism spectrum classification in earlier editions of the Diagnostic and Statistical Manual of Mental Disorders (DSM). However, in the latest edition (DSM-5), the term PDD-NOS has been replaced with the broader category of Autism Spectrum Disorder (ASD). Nevertheless, it’s worth discussing what PDD-NOS used to encompass.

PDD-NOS was a diagnosis given to individuals who displayed some, but not all, of the characteristics associated with Autism Spectrum Disorders. Individuals diagnosed with PDD-NOS typically exhibited social and communication challenges, as well as repetitive behaviours, but the symptoms were not as severe or did not fit neatly into the criteria for Autistic Disorder or Asperger’s Syndrome. PDD-NOS was often considered a “catch-all” category for individuals who did not fully meet the criteria for other specific autism spectrum diagnoses.

The symptoms of PDD-NOS could vary widely, and the level of impairment in social interaction, communication, and behaviour might be less pronounced than in other forms of ASD. The shift to the umbrella term “Autism Spectrum Disorder” in DSM-5 reflects a recognition of the diverse and overlapping nature of symptoms within the spectrum, acknowledging that individuals may present with a wide range of challenges and strengths. As such, the term PDD-NOS is no longer used in current diagnostic practice.

Childhood Disintegrative Disorder (CDD)

Childhood Disintegrative Disorder (CDD), also known as Heller’s syndrome, is a rare and severe developmental disorder that falls under the broader umbrella of Autism Spectrum Disorder (ASD). CDD is characterised by a significant loss of previously acquired skills and abilities in multiple areas of development, including language, social skills, motor functions, and adaptive behaviours. The onset of symptoms typically occurs after a period of normal development, usually between the ages of 2 and 10, and the regression can be rapid and profound.

Children with Childhood Disintegrative Disorder may initially develop typically, reaching milestones in language, social interaction, and motor skills. However, they experience a noticeable and severe regression in these areas, leading to a loss of skills they had previously acquired. This regression often involves the loss of language skills, social engagement, toileting skills, and motor coordination. The deterioration can be so significant that affected children may become nonverbal, lose bladder and bowel control, and withdraw from social interactions.

The exact cause of Childhood Disintegrative Disorder is not well understood, and the prognosis is generally poor. While some researchers believe there may be a neurological basis for CDD, the precise mechanisms remain unclear. Early intervention and supportive therapies are crucial, although the level of improvement can vary widely among individuals. Due to the rarity of CDD, affected individuals and their families need to work closely with healthcare professionals to develop individualised treatment plans and support strategies.

Levels 1, 2, and 3

The levels of Autism Spectrum Disorder (ASD) are specified in the DSM-5 (Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition) to help describe the severity of the condition based on the level of support an individual may need. Here are the three levels along with examples:

Level 1: Requiring Support

Individuals with Level 1 ASD, often referred to as “mild” ASD, require some support to navigate social situations and daily life. While they may have noticeable challenges in social communication, repetitive behaviours, and flexibility, these difficulties may not be severe enough to significantly impair functioning. Examples of behaviours associated with Level 1 ASD may include difficulties initiating and sustaining social interactions, limited interest in peers, and challenges with transitions or changes in routine. Some individuals at this level may have special interests that dominate their conversations, making it challenging to engage in reciprocal communication.

Level 2: Requiring Substantial Support

Individuals with Level 2 ASD, categorised as “moderate” ASD, demonstrate more pronounced challenges in social communication and behaviour. They require substantial support to navigate social interactions and daily activities. These individuals may exhibit more marked deficits in verbal and nonverbal communication, struggle with initiating social interactions, and show inflexibility to changes in routine. Some may engage in repetitive behaviours that interfere with daily functioning. Individuals at this level often benefit from more structured environments and tailored interventions to address their specific needs.

Level 3: Requiring Very Substantial Support

Level 3 ASD, often termed “severe” ASD, is characterised by significant impairments in social communication and behaviour, requiring very substantial support. Individuals at this level may have limited verbal communication or be nonverbal, and they often struggle with basic social interactions. Repetitive behaviours may be more prominent and can interfere significantly with daily functioning. These individuals may also have difficulty adapting to changes in routine and may exhibit challenging behaviours that necessitate careful management and support. Intensive and individualised interventions are typically required to address the complex needs associated with Level 3 ASD.

Moreover, these levels are meant to provide a general framework and that individuals with ASD are unique, with a wide range of strengths and challenges. The goal is to tailor support and interventions to the specific needs of each individual.


ASD Summary

In conclusion, Autism Spectrum Disorder (ASD) encompasses a diverse range of conditions, each with its unique characteristics and challenges. Classic Autism, characterised by significant impairments in social interaction, communication, and repetitive behaviours, often requires early intervention and tailored support to enhance outcomes. Asperger’s Syndrome, marked by social difficulties and restricted interests, typically involves individuals with normal to above-average intelligence who may benefit from strategies to navigate social situations.

Childhood Disintegrative Disorder (CDD), though rare, presents a severe form of ASD, where individuals experience a rapid loss of previously acquired skills. The prognosis for CDD is generally poor, necessitating individualised treatment plans and early intervention.

The former diagnostic category of Pervasive Developmental Disorder-Not Otherwise Specified (PDD-NOS) has been replaced by the broader term Autism Spectrum Disorder (ASD) in the current DSM-5, reflecting the recognition of the spectrum’s diversity.

The severity levels within ASD (Levels 1, 2, and 3) help characterise the extent of support individuals may need. Tailored interventions, such as speech and language therapy, occupational therapy, and behavioural interventions, are critical across all levels. Early intervention, individualised treatment plans, and family support play pivotal roles in maximising the potential and improving the quality of life for individuals with ASD. Therapies aim to address specific challenges, such as social communication deficits, sensory sensitivities, and repetitive behaviours, fostering independence and enhancing overall well-being. As our understanding of ASD evolves, ongoing research and a multidisciplinary approach continue to contribute to the development of effective interventions and support strategies for individuals across the autism spectrum.

Next Steps

If you suspect that you or someone you know may be on the autism spectrum, seeking an Autism Spectrum Disorder (ASD) assessment is a crucial step towards understanding and addressing unique needs. A timely and accurate diagnosis can pave the way for tailored interventions, support, and resources that can significantly improve outcomes.

To take action:

Consult with Healthcare Professionals
Reach out to your primary care physician, paediatrician, or a healthcare professional who specialises in developmental disorders. Discuss your concerns openly and provide detailed information about observed behaviours and developmental milestones.

Seek Referral to Specialists
Based on your discussions, your healthcare provider may refer you to specialists such as developmental paediatricians, child psychologists, or neurologists who can conduct a comprehensive ASD assessment. These assessments often involve observations, interviews, and standardised tests to evaluate various aspects of development.

Connect with Autism Specialists
Locate professionals specialising in autism assessment, such as clinical psychologists, neuropsychologists, or developmental specialists. These specialists can conduct in-depth evaluations to determine whether an individual meets the criteria for an ASD diagnosis.

Contact Educational Institutions
If you are concerned about a child’s development, reach out to their school or educational institution. School psychologists and special education professionals can play a vital role in the assessment process and collaborate with healthcare providers to ensure a holistic understanding of the individual’s needs.

Engage Support Organisations
Connect with local autism support organisations, advocacy groups, or community resources. They can provide guidance on the assessment process, share information about available services, and offer support to individuals and families navigating the ASD journey.

Remember, early intervention is key, and seeking an ASD assessment can provide valuable insights into an individual’s strengths and challenges. By taking proactive steps, you empower yourself or your loved one with the information needed to access appropriate support, interventions, and resources for a more fulfilling and enriched life.