Since 2013, there is officially one form of autism: autism spectrum disorder (ASD). Before that, clinicians diagnosed several separate conditions that are now folded under this single diagnosis. The change reflects a modern understanding that autism isn’t a collection of distinct disorders but one condition with a wide range of presentations, from people who need minimal day-to-day support to those who need help with basic communication and self-care.
The Old Subtypes That No Longer Exist
Before 2013, the American Psychiatric Association recognized four separate diagnoses that would all be considered autism today:
- Autistic disorder was the “classic” autism diagnosis, typically given to children with significant language delays, social difficulties, and repetitive behaviors.
- Asperger syndrome was used for people with strong verbal skills and average or above-average intelligence who still had notable social difficulties and intense, narrow interests. Many people diagnosed during this era still identify with the term.
- Pervasive developmental disorder not otherwise specified (PDD-NOS) was a catch-all for people who had some but not all features of autistic disorder. It was sometimes called “atypical autism.”
- Childhood disintegrative disorder was a rare condition in which a child developed typically for at least two years and then lost previously acquired language, social, and motor skills.
The boundaries between these categories were blurry in practice. Two children with very similar traits could receive different diagnoses depending on the clinician, the assessment tools used, or even their geographic location. Merging them into a single spectrum diagnosis was meant to improve consistency and ensure that everyone with autism-related traits had access to the same services regardless of which label they happened to receive.
Why One Spectrum Replaced Multiple Diagnoses
The shift happened when the DSM-5 (the diagnostic manual used by mental health professionals in the United States) was published in 2013. The new framework recognizes autism through two core areas rather than through separate named conditions. To receive a diagnosis, a person must show persistent difficulties in all three aspects of social communication and interaction: social-emotional reciprocity (the back-and-forth of conversation and shared attention), nonverbal communication (eye contact, gestures, facial expressions), and building and maintaining relationships.
They must also show at least two of four types of restricted or repetitive behaviors: repetitive movements or speech, insistence on sameness and rigid routines, intensely focused interests, or unusual reactions to sensory input like sounds, textures, or light. Symptoms need to be present from early childhood, though they may not become obvious until social demands outpace a person’s coping strategies. This is why some people, particularly women and girls who learn to mask their traits, aren’t diagnosed until adolescence or adulthood.
The Three Support Levels
Instead of separate diagnoses, the current system assigns one of three support levels at the time of evaluation. These levels are rated independently for each of the two core areas, so a person might have Level 1 support needs for social communication but Level 2 for repetitive behaviors.
Level 1, sometimes described as “requiring support,” applies to people who can communicate in full sentences and manage much of daily life independently but struggle with social nuances. They may have difficulty initiating conversations, reading social cues, or switching between tasks. Without some support, these challenges cause noticeable problems at work, school, or in relationships.
Level 2, “requiring substantial support,” describes people with more pronounced social communication difficulties even with support in place. A child at this level might, for example, become intensely focused on a favorite topic to the point where redirecting to schoolwork causes significant distress. Flexibility with routines is harder, and social interactions are more limited.
Level 3, “requiring very substantial support,” applies to people with the highest support needs. A child diagnosed at this level might not yet use words or gestures to communicate their needs. They may spend much of their time engaged in repetitive activities like lining up objects and become very distressed when interrupted. Daily living requires consistent, hands-on help.
These levels are not permanent labels. A person’s support needs can change over time with development, therapy, life circumstances, or the demands of a new environment. They’re best understood as a snapshot of where someone is at the moment of diagnosis, not a prediction of where they’ll always be.
Why No Two Autistic People Look the Same
One reason the old subtypes broke down is that autism varies enormously from person to person. Two people both diagnosed at Level 1 may have completely different strengths, challenges, and daily experiences. One might be highly verbal but overwhelmed by fluorescent lighting and background noise. Another might handle sensory input well but find the unspoken rules of workplace small talk nearly impossible to navigate.
Nearly 70% of autistic people also have at least one co-occurring mental health condition, and about 40% have two or more. Anxiety disorders, ADHD, depression, and mood disorders are all common. These overlapping conditions shape how autism shows up in daily life, sometimes making it harder to identify the autism itself. A child whose primary visible struggle is hyperactivity or anxiety might not be evaluated for autism until years later, for instance.
Profiles Within the Spectrum
Even though there are no official subtypes, clinicians and researchers sometimes use informal profiles to describe patterns they see frequently. One example is pathological demand avoidance (PDA), a behavioral pattern most often observed in autistic people. Children with PDA go to extremes to avoid anything they perceive as a demand, even everyday tasks they’re perfectly capable of doing, like putting on shoes or sitting at a table. The avoidance can look like making excuses, creating distractions, withdrawing, or having a meltdown. A key feature is that these children tend to complete tasks only when they’re personally motivated rather than when asked.
PDA is not a separate diagnosis or an official subtype of autism. It’s better understood as a description of behavior that can guide parents and teachers toward strategies that work, particularly approaches that emphasize flexibility and reduce the feeling of external pressure. Some researchers have speculated it reflects a neurological difference, but there isn’t empirical evidence for that yet. The avoidance often has varied underlying causes from child to child, including difficulty with executive functioning, which makes it hard to anticipate and adapt to expectations that weren’t self-chosen.
How Autism Is Assessed Today
Because autism now exists on a single spectrum with so much variation, diagnosis relies on thorough, individualized evaluation rather than a simple checklist. The gold-standard observational tool is the ADOS-2 (Autism Diagnostic Observation Schedule, Second Edition), which uses specific activities and materials to create both structured and unstructured social situations. A trained examiner watches how the person responds spontaneously and when prompted, rating their social engagement, communication, and behavior patterns. This is typically paired with the ADI-R (Autism Diagnostic Interview, Revised), a detailed caregiver interview that captures developmental history.
These tools require extensive training to administer and interpret, which is one reason wait times for autism evaluations can stretch to months or even years in some regions. The goal is to capture the full picture of a person’s abilities and challenges so the diagnosis reflects not just whether someone is autistic but what kind of support would actually help them.