Delayed Autism Diagnoses: Common Reasons and What to Do

Autism is a spectrum disorder, meaning each individual may display a unique combination of traits and behaviours. Because of this wide variability, some people may be diagnosed later in life.

Even if common signs associated with autism (ASD) become more noticeable later, it is never too late to seek a diagnosis. Obtaining a proper assessment can open the door to the right support, personalised interventions, and access to resources that help improve developmental outcomes and overall well-being.

The Challenge of a Quick Diagnosis

Despite growing awareness of autism, many individuals still encounter challenges in obtaining a timely diagnosis. While detection is often associated with children as young as 18 months, this is not always the case.

Children with more noticeable traits may initially receive alternative diagnoses, such as Attention Deficit Hyperactivity Disorder (ADHD) or sensory processing issues. While these can coexist, they do not fully address the unique needs of children with autism, making a formal autism evaluation essential.

In other cases, children may intentionally mask or camouflage their autistic traits in order to “fit in” socially. This masking behaviour often leads parents, teachers, and even clinicians to overlook signs of autism, resulting in further delays in diagnosis and support.

Why Autism Is Overlooked in Early Screenings

Autism screening typically happens during routine check-ups and developmental assessments. However, many factors can cause autism to be missed. These are some of the reasons why autism is diagnosed so late or why it seems to show up later:

1. Clinicians’ Hesitation to Diagnose

Doctors may be cautious about providing a formal autism diagnosis, particularly for very young children. This is because autism is a lifelong condition, and clinicians want to ensure that any diagnosis is accurate before communicating it to families.

That’s why their initial approach is to address a milder or less severe condition first, such as a speech delay, ADHD, or behavioural difficulties, and then reassess the child over time.

2. The “Wait-and-See” Approach

Studies show that some paediatricians tend to adopt a “wait-and-see” approach when developmental concerns arise. While some may encourage parents to bring their child for a screening, they may not always follow up on the results or promptly recommend early intervention.

Although the intention is often to give the child time to catch up with their neurotypical peers, this approach can unintentionally affect the child’s well-being. Delaying further assessment or therapy can widen developmental gaps and long-term health disparities, particularly in the child’s emotional and mental well-being.

3. The Time-Intensive Assessment Process

Another reason why individuals get misdiagnosed is the time it takes to get a diagnosis. As highlighted by Healthline, there is no single lab test or brain scan that can definitively diagnose autism. Instead, diagnosis relies heavily on observing how the person behaves and communicates, as well as their developmental history. In other words, healthcare professionals must assess whether an individual consistently demonstrates traits associated with autism.

Because of this, comprehensive evaluations often require multiple observations, structured assessments, and input from caregivers or teachers. For children with milder or less obvious autism signs, this process is even more time-consuming. As a result, some children may receive an incomplete assessment.

4. The Misinterpretation of Manifestations

Because autism presents differently in every individual, it is often misunderstood, leading to misdiagnoses or missed diagnoses.

For instance, delayed autism diagnosis is especially common among women in Singapore, who may develop stronger social masking skills. They may learn to imitate socially appropriate communication styles or rehearse conversations before social interactions. These strategies help them camouflage their condition and blend in with their peers.

However, while these skills may give the initial appearance of coping well socially, signs of autism often become more apparent later on, impacting academic work, professional environments, or daily functioning. And when their autism remains unidentified or is diagnosed late, they could potentially experience significant consequences, such as chronic stress, burnout, and mental health difficulties.

5. Focus on Other Conditions

When misdiagnosis or underdiagnosis occurs, the healthcare professional will focus on the most obvious presenting issue, whether that is speech or language delays, sensory processing challenges, or behavioural or emotional challenges.

While these concerns are valid, focusing exclusively on them can obscure the broader picture of autism, delaying the initiation of tailored autism therapy in Singapore.

6. Socioeconomic Barriers

Financial, logistical, or social challenges may also be another reason why it could be difficult to get an autism diagnosis. Factors that contribute include:

• Limited access to private assessments or specialists
• Long wait times at public hospitals
• Barriers in coordinating multiple appointments
• Limited awareness of available support services

Socioeconomic barriers can prevent children from receiving timely interventions, which are critical in the early years for optimal developmental outcomes.

Other Reasons for Delays in Autism Diagnosis

Aside from overlooked evaluations, other factors may contribute to the delayed autism diagnosis, including:

1. Later Onset of Signs

While autism does not develop later in life, some individuals could experience a delayed diagnosis due to high-functioning traits or effective coping strategies in childhood. As such, the appropriate term for this may be “late-identified” autism rather than later onset. This could occur due to various reasons, including:

• Prolonged masking or camouflaging behaviours
• Limited awareness or outdated knowledge about autism, especially regarding girls and high-masking individuals
• Diagnostic tools and criteria that are less sensitive to subtle or non-traditional presentations
• Functional challenges that emerge later, such as difficulties with independence, executive functioning, or managing complex social demands in adolescence or adulthood

2. Parental Denial or Shame

Stigma surrounding developmental conditions can also slow the diagnostic process. Some researchers found that many parents experience fear, shame, or worry about being judged for their child’s behaviours.

When parents witness other families face criticism or misunderstanding, they may:

• Delay seeking an assessment
• Attribute their child’s behaviours to personality traits or parenting styles
• Hope the child will “grow out of it”
• Avoid discussing concerns with teachers or healthcare professionals

This hesitation can postpone early intervention that would otherwise support the child’s development.

3. Co-occurring Conditions

Autism often occurs alongside other developmental or mental health conditions, such as sensory processing challenges, and even mental health issues like anxiety or depression. These co-occurring conditions can overshadow or complicate the autism presentation.

For example, a child may receive treatment for anxiety or ADHD while the underlying autism remains unrecognised. When multiple conditions overlap, the diagnostic process becomes more complex and may require longer, multidisciplinary evaluations.

The Autism Diagnostic Process

While the diagnostic journey may vary, a comprehensive autism evaluation generally includes several key steps. Understanding these can help parents navigate the process more confidently.

1. Parental Monitoring of Development

Parents are often the first to notice when something feels different in their child’s development.

Monitoring early milestones, such as language growth, eye contact, social engagement, play behaviour, and emotional regulation, is an important first step.

Even subtle signs can be meaningful, including:

• Difficulty with transitions or changes in routine
• Limited or unusual pretend play
• Repetitive movements or interests
• Strong reactions to sensory input, such as noise, textures, and lights
• Delayed speech or atypical communication styles

If something doesn’t feel quite right, parents are encouraged to trust their instincts and consult a healthcare professional early. Early discussions allow potential concerns to be addressed before more significant challenges emerge.

2. Recommended Screenings

Paediatricians are a major contributor to early identification. Routine developmental screenings, often conducted during well-child visits, help identify early signs of autism and other developmental differences.

When selecting a paediatrician, parents should ensure that the doctor:

• Conducts regular developmental and behavioural screenings
• Uses validated screening tools for toddlers
• Provides clear follow-up steps when concerns arise
• Encourages timely referrals for specialist evaluation rather than adopting a “wait-and-see” approach

These screenings do not provide a diagnosis, but they guide the next steps by determining whether a more comprehensive evaluation is needed.

3. Comprehensive Evaluation and Testing

If screening results or parental concerns suggest the need for further assessment, a full diagnostic evaluation will be recommended. This is typically carried out by a multidisciplinary team that may include psychologists, developmental paediatricians, speech-language therapists, or occupational therapists.

A comprehensive evaluation may involve:

• Developmental history interviews with parents or caregivers
• Direct observation of the child’s behaviour and play
• Standardised assessments measuring communication, social interaction, cognitive skills, and adaptive behaviour
• Reports from teachers or childcare providers for additional insight across settings
• Medical assessments to rule out other underlying conditions

This holistic approach ensures that the child’s strengths, needs, and challenges are accurately understood, supporting the development of a tailored intervention plan.

Get the Support Your Child Needs with Exploring Mates

A delayed autism diagnosis should not hinder your child from getting assessed or receiving the help they need. Whether your child is younger or older than 2 years old, early signs should always be evaluated by a qualified professional. With the appropriate diagnosis, children can access the supports and interventions that help them thrive.

If your child requires autism therapy, early communication intervention, and education support, our private early intervention centre is ready to support your family. Exploring Mates provides a range of evidence-based programmes for children with autism and developmental delays, helping them build essential communication, social, behavioural, and learning skills.