Why is autism so often misdiagnosed? And how can autism be mistaken for something like borderline personality or schizophrenia, which seem so very different from autism?

The harms of misdiagnosis are significant, including unnecessary stigma, long-term masking, harmful side effects from unneeded medications, and even reduced life expectancy (Eaton, 2024).

As consequential as misdiagnosis is, it remains common: One in four Autistic adults (one in three Autistic women) report mental health diagnoses that preceded their autism diagnoses (Kentrou et al., 2024). While some of those prior mental health diagnoses may have been accurate, the injurious fact remains that their autism was missed. Not only did they not receive the care or support they needed for autism, but any genuine mental health conditions were treated outside the context of autism, that is to say, incompletely.

Let’s take a look at some of the most common misdiagnoses of autism, why they happen, and how we might spot them to better advocate for ourselves and our children.

1. Attention-Deficit Hyperactivity Disorder (ADHD)

As many as 70% of Autistic people also have ADHD (Hours et al., 2022). AuDHD, as the combination is colloquially called, may in fact be more common than one or the other alone. While some researchers speculate that certain autism traits can be mistaken for ADHD traits—for example, social difficulties being attributed to inattention—most of the misdiagnosis research focuses on co-occurring ADHD and autism.

In this group, autism diagnoses are commonly delayed or missed altogether. W. Sainsbury et al., 2022 found that “ASD is typically diagnosed later when ADHD is present, and ADHD is typically diagnosed earlier when ASD is present,” indicating that ADHD can mask ASD. This also supports the common anecdotal observation of autism being recognized only after initiating ADHD medication.

2. Borderline Personality Disorder (BPD)

Autism co-occurring with depression, anxiety, or ADHD may make diagnosis challenging, but the most common cause of autism being misdiagnosed as BPD is the superficial but numerous shared presentations. Those presentations, however, do not share causes or remedies.

This misdiagnosis, while common, can usually be avoided by experienced clinicians providing a thorough assessment. The following overlaps have led to Autistic people being misdiagnosed with BPD:

• Non-suicidal self-harm (Powell et al., 2024).
• Meltdown (McQuaid et al., 2024).
• Shutdown (Tamilson et al., 2024).
• Identity or self-concept issues (McQuaid et al., 2024).
• Social and interpersonal differences (McQuaid et al., 2024).

How does one differentiate? Most of these presentations in an Autistic person will have sensory triggers and remedies. In BPD, triggers and remedies are typically relational. Because the individual experience of having each of these conditions is so distinct from that of the other, it is—as always—crucial to listen to patients and believe their lived experiences.

3. Schizophrenia

M. Woodbury-Smith et al., 2010 write that “a significant number of adults may have an undiagnosed autism spectrum disorder” and “some of these will have been managed in mental health services and treated for a psychotic disorder.” It may seem hard to believe that autistic traits could be mistaken for symptoms of psychosis, but consider the following examples:

• Double empathy: An undiagnosed Autistic adult is struggling to interpret neurotypical communication subtleties at work and shares with their therapist that they suspect everyone is talking about them (M. Woodbury-Smith et al., 2010). The therapist thinks: paranoia.
• Cognitive rigidity: When the therapist attempts a reality check on this interpretation, the client insists on their observation with increasing agitation (M. Woodbury-Smith et al., 2010). The therapist now suspects a delusion.
• Literal misunderstanding: An undiagnosed Autistic teen’s parents take her to the doctor after a major meltdown. The doctor asks if she hears voices. She says yes, because she can hear the doctor’s voice right now (Happé, 2012). The doctor notes in the teen’s medical chart that she hears voices.
• Burnout: The teen’s parents describe to the doctor her recent presentation of poor motivation and social withdrawal. Taken together with her stating that she hears voices, the doctor interprets this as the “negative symptoms” associated with schizophrenia.

4. Social Anxiety Disorder (SAD)

Both autism and social anxiety disorder have social differences as primary presentations, and indeed, they can be difficult to distinguish from one another. N. Tonge et al., 2015 found that 70.8% of individuals diagnosed with generalized social anxiety disorder self-reported more autistic traits, pointing to significant symptom overlap. Shared traits may include difficulties with (Spain et al., 2018):

Autistic individuals, in contrast to those with social anxiety disorder, experience sensory sensitivities and environmental mismatch (Wilson & Gullon-Scott, 2024), which refers to the broader stressful experience of navigating a neurotypical world with a neurodivergent brain.

5. Oppositional Defiance Disorder (ODD)

ODD is most commonly diagnosed in children. Clinicians use three-dimensional groups of traits and behaviors to diagnose ODD, and all three were found present and measurable in a study of 216 verbally fluent Autistic children (Mandy et al., 2013). Those dimensions are (Santiago, 2013):

• Angry/irritable mood: losing temper, easily annoyed, often angry or resentful.
• Argumentative/defiant behaviors: arguing with authority figures, defying rules or requests, intentionally annoying others, blaming others for mistakes.
• Vindictiveness: seeking revenge, saying mean or hateful things, spitefully sabotaging others’ efforts, holding malicious grudges.

Any parent of a neurodivergent child, especially one identified as having a PDA profile (pathological demand avoidance / persistent drive for autonomy), will likely recognize a few of their child’s behaviors in the above list. And the reality is that this is likely the muddiest distinction of the five we’ve covered here.

Many Autistic children do have clinically significant ODD traits (Gadow et al., 2008) and may receive an additional diagnosis of ODD, although this is controversial. Whether ODD represents a co-occurring, separate condition in Autistic kids, a distinct phenotype of autism, or a set of traits inherent to autism is not established. Perhaps the best clinicians can do right now is to not miss an autism diagnosis.

Closing Thoughts

Across all five of these misdiagnoses, we see a through-line: while presentations may look similar, the causes and care are different. Getting it right starts with clinical autism awareness, and with believing people when they describe their own experiences.

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