Can Autism Cause Delusions or Co-Occurring Conditions?

Autism does not directly cause delusions, but autistic people experience psychotic symptoms at notably higher rates than the general population. A meta-analysis estimated that roughly a quarter of autistic individuals report some form of psychotic experience, and autistic traits across the broader population show a consistent positive correlation with such experiences. Beyond psychosis, autism co-occurs with a wide range of psychiatric and medical conditions, from anxiety and ADHD to epilepsy and gastrointestinal problems, at rates that go well beyond coincidence. Untangling what autism itself produces, what it predisposes a person toward, and what gets mistakenly attributed to it is one of the trickier problems in clinical practice.

Psychotic Experiences and Delusions in Autistic People

The relationship between autism and delusions is real but messy. A systematic review and meta-analysis found that the pooled prevalence of psychotic experiences in people with autism was about 24%, with a wide confidence interval reflecting how much rates vary across studies. When the authors broke this down by type, hallucinations appeared in roughly 6% of autistic individuals, while delusion estimates were far more variable and harder to pin down.¹ Separately, a meta-analysis focused specifically on schizophrenia spectrum disorders in autistic adults with average IQ found a pooled prevalence of close to 6%, considerably higher than in the general population.²

One reason the delusion numbers are so unstable is that distinguishing a true delusion from certain autistic thought patterns is genuinely difficult. A delusion, in the clinical sense, is a fixed false belief held with conviction despite contradictory evidence. But autistic individuals sometimes hold rigid beliefs, engage in elaborate fantasy worlds, or interpret social situations in idiosyncratic ways that look delusional on the surface but have different roots. As one review put it, the line between “childish fantasies” and delusional beliefs can be blurry in practice.³ A person who takes social cues literally, or who constructs a detailed internal narrative to make sense of confusing social interactions, can appear paranoid or delusional without meeting the clinical definition.

Why Paranoia Shows Up More Often

Paranoia is elevated in autistic people compared to the general population, though not as high as in people with paranoid schizophrenia. A systematic review found that autistic participants consistently reported higher levels of paranoia than non-clinical controls, while scoring lower than people diagnosed with paranoid schizophrenia and higher than those with non-paranoid schizophrenia.⁴ The same review found that paranoia scores in autistic people were negatively correlated with theory-of-mind performance, meaning those who had more difficulty reading others’ mental states tended to report more paranoid thinking.

This makes intuitive sense. If you consistently struggle to read facial expressions, detect sarcasm, or understand why people behave the way they do, the social world becomes unpredictable. One reasonable response to chronic social unpredictability is suspicion. The paranoia many autistic people describe is not the elaborate conspiratorial thinking seen in psychotic disorders but rather a persistent wariness rooted in genuinely confusing social experiences and, often, a history of being bullied or excluded.

Sensory Processing and Hallucinations

Unusual sensory experiences are a core feature of autism, and they sometimes get mistaken for hallucinations. A person who reports hearing sounds others do not may have sensory hypersensitivity rather than auditory hallucinations. A study of children and adolescents found that sensory processing difficulties were significantly associated with hallucinations even after controlling for autism diagnosis, age, sex, and mood disorders. Interestingly, autism itself did not show a significant independent association with hallucinations in that study once sensory processing was accounted for.⁵

This finding suggests that the sensory processing differences common in autism may be a pathway to hallucination-like experiences, but the connection runs through sensory sensitivity rather than through autism per se. For clinicians, the practical implication is that an autistic person reporting unusual perceptual experiences needs careful assessment before anyone assumes psychosis. Sensory overload, misidentified sounds in noisy environments, and vivid mental imagery can all look like hallucinations in a brief clinical interview.

The Historical Tangle with Schizophrenia

Part of the confusion stems from the fact that autism and childhood schizophrenia were once treated as the same diagnosis. Before the DSM-III was published in 1980, children who would now be diagnosed with autism were frequently labeled as having childhood schizophrenia. Many of the symptoms described in that older literature, including ritualistic behavior, dislike of novel situations, monotone speech, and non-functional play, map directly onto what we now recognize as core autistic traits.⁶ When the DSM-III introduced autism as a separate diagnosis, it was explicitly meant to replace childhood schizophrenia.

At the genetic level, the relationship between autism and schizophrenia is more complicated than simple overlap. Research on copy-number variants in the genome found evidence that at several genetic locations, deletions predispose to one condition while duplications at the same spot predispose to the other, a pattern sometimes described as reciprocal or diametric rather than overlapping.⁷ So while both conditions involve altered brain development, they are not simply different severities of the same thing. They share some genetic territory but occupy partly opposing positions within it.

Anxiety Disorders

Anxiety is probably the most common psychiatric co-occurrence in autism, and it affects daily life enormously. A meta-analysis of autistic youth found that about a third reported elevated anxiety symptoms on self-report measures, with diagnostic interviews identifying anxiety disorders in roughly one in five.⁸ In adults, the picture is similar: a population-based study found that about 20% of autistic adults had a diagnosed anxiety disorder, compared with under 9% of the general adult population. OCD was especially overrepresented, appearing at more than eight times the rate seen in non-autistic adults.⁹

The OCD finding deserves extra attention because autistic repetitive behaviors and OCD compulsions can look almost identical from the outside. Both involve rigid routines, intense focus on specific topics, and distress when routines are disrupted. A comparative review found that while the developmental trajectories of repetitive behaviors in autism and OCD share some similarities, the role of anxiety is a key distinguishing factor. In OCD, the repetitive behavior is typically driven by anxiety and the person wants to stop. In autism, repetitive behaviors are more often self-soothing or pleasurable, and the distress comes from being forced to stop rather than from the behavior itself.¹⁰ Both conditions can coexist in the same person, which makes clinical assessment challenging.

ADHD and Executive Function

ADHD and autism overlap so frequently that the DSM-5 dropped its previous rule against diagnosing both in the same person. The two conditions share deficits in executive functioning, but not always the same ones. A review found that when both conditions are present, the combined profile includes the planning and flexibility problems typical of autism alongside the response-inhibition deficits characteristic of ADHD, suggesting the co-occurrence reflects an additive combination rather than a wholly separate condition.¹¹ A study of autistic children found that most parent and teacher ratings of executive functioning problems tracked with ADHD symptom severity rather than autism severity, except in the areas of emotional control and cognitive flexibility, which appeared related to autism itself.¹²

For a person living with both conditions, the practical effect is a compounding of difficulties. The organizational challenges of ADHD layer on top of the rigidity and social demands of autism. Recognizing ADHD as a separate contributor matters because ADHD-specific interventions, including medication, can improve functioning in ways that autism-focused approaches alone do not.

Trauma, PTSD, and Autistic Burnout

Autistic people are more vulnerable to post-traumatic stress, and the reasons go beyond simply being exposed to more adverse events (though that happens too). A study comparing autistic and non-autistic adults found that autistic participants had significantly higher PTSD symptom severity and were more likely to endorse negative post-traumatic appraisals, particularly feelings of alienation, shame, and fear.¹³ The way autistic people process and interpret threatening experiences appears to amplify the psychological impact.

Related but distinct from PTSD is the concept of autistic burnout, which has gained recognition as a state of chronic exhaustion and reduced functioning linked to the sustained effort of masking autistic traits in social settings. Research has connected camouflaging behaviors to suicidal thoughts and behaviors, with burnout proposed as a mediating pathway: the prolonged stress of passing as neurotypical wears a person down, worsening mental health over time.¹⁴ Burnout can look like depression, and it frequently gets diagnosed and treated as depression, but it has different triggers and may need different responses, particularly reduced social demands rather than activation-focused therapy.

Epilepsy, Sleep, and Gut Problems

The co-occurring conditions in autism are not limited to psychiatric diagnoses. Epilepsy affects roughly one in ten autistic individuals according to a meta-analysis, with higher rates in adolescents, adults, females, and those with intellectual disability.¹⁵ The overlap almost certainly reflects shared underlying neurodevelopmental factors rather than one condition causing the other.¹⁶

Sleep disturbances are pervasive. Research has found that autistic individuals tend to have lower nighttime melatonin levels, and both functional and genetic variations in the melatonin pathway have been reported in autistic children.¹⁷ A study of autistic children and adolescents showed that those who had not yet reached puberty had delayed onset of melatonin production, while adolescents showed an earlier decline, and these melatonin timing differences were linked to delayed sleep onset and lower daytime activity levels.¹⁸ This is not garden-variety insomnia but a biological difference in circadian regulation.

Gastrointestinal problems round out the picture, with estimates suggesting that up to 80% of autistic children experience some form of GI difficulty.¹⁹ Constipation, diarrhea, and abdominal pain are common complaints. For non-speaking autistic children, these problems can manifest as behavioral changes rather than verbal complaints, which leads to underdiagnosis.

Catatonia and Alexithymia

Catatonia is an underrecognized complication in autism. It typically emerges in late adolescence and involves a dramatic slowing or cessation of movement, mutism, and sometimes rigid posturing. The overlap in symptoms between catatonia and autism is substantial, as both can involve mutism, echolalia, stereotyped movements, and unusual postures. The distinguishing feature is timing: catatonic symptoms are typically new-onset or represent a sharp worsening of existing behaviors, whereas the autistic traits they resemble have been present since early childhood.²⁰ Because clinicians unfamiliar with this overlap tend to attribute worsening motor symptoms to autism itself, catatonia in autistic people frequently goes untreated.

Alexithymia, the difficulty identifying and describing one’s own emotions, is another common companion to autism that shapes how other conditions present. Research has found that in autistic individuals, higher alexithymia scores were associated with less empathic concern for others but greater personal distress when witnessing others’ pain.²¹ Alexithymia complicates the diagnosis and treatment of almost every co-occurring mental health condition because standard clinical tools rely heavily on a person’s ability to report their emotional state. If you cannot put names to your feelings, screening questionnaires for depression and anxiety become unreliable.

Diagnostic Overshadowing and Misdiagnosis

One of the biggest practical problems is that autism tends to overshadow everything else. When clinicians know a person is autistic, they may attribute new symptoms to autism rather than investigating a separate co-occurring condition. The reverse is equally common: before an autism diagnosis is made, autistic traits get misread as other psychiatric conditions. A large survey found that about a quarter of autistic adults reported at least one prior psychiatric diagnosis they believed was a misdiagnosis, with women roughly twice as likely as men to report this experience.²²

Women are hit especially hard by this pattern. Autistic women without intellectual disability are frequently underdiagnosed because their social presentations tend to be subtler, their compensatory strategies more polished, and standard screening tools less sensitive to female-typical autistic traits. These women are more likely to accumulate psychiatric diagnoses, including personality disorders, mood disorders, and eating disorders, before anyone considers autism.²³ A study tracking what happened after autistic adults received their autism diagnosis found that women were significantly more likely than men to have prior diagnoses that effectively disappeared once autism was identified, including personality disorders at over four times the rate and eating disorders at nearly nine times the rate.²⁴

Gender Differences in What Co-Occurs

Beyond the misdiagnosis problem, genuine differences exist in which conditions autistic men and women tend to develop. A systematic review and meta-analysis found that autistic women had higher rates of anxiety, eating disorders, and trauma-related conditions, while autistic men showed elevated rates of certain externalizing and neurodevelopmental conditions.²⁵ Whether these differences reflect biology, differential social pressures, or the consequences of later diagnosis in women is still being sorted out. The practical takeaway is that a clinician evaluating an autistic woman for co-occurring conditions should be especially attentive to anxiety, eating pathology, and trauma history, while evaluations of autistic men should screen carefully for ADHD and conduct-related difficulties.

Treatment Sensitivities

Treating co-occurring conditions in autistic people comes with its own complications. On the medication side, a systematic review and meta-analysis found that adverse events from antipsychotic treatment were about 22% more likely in autistic individuals than with placebo, with an estimated overall side-effect rate above 50%. The most common problems were increased appetite and weight gain, which drove many people to stop treatment.²⁶ The most-studied antipsychotics for neurodevelopmental conditions remain aripiprazole and risperidone, and the side-effect profile across studies consistently includes metabolic problems, sedation, and hormonal changes.²⁷

Psychological treatments need adaptation too. Cognitive behavioral therapy shows moderate effectiveness for anxiety and depression in autistic adults, but reviews consistently note that standard protocols require modification. Adaptations include more sessions, greater use of visual and concrete materials, and explicit accommodation of the ways autistic people process information and emotion.²⁸ A study from an NHS service found that adapted low-intensity CBT was associated with reduced anxiety and depression scores for autistic adults, with one-to-one delivery and anxiety-focused treatment performing better than group formats.²⁹ The consistent theme is that off-the-shelf mental health treatments can work for autistic people, but they often need to be rebuilt from the inside to account for different communication styles, sensory needs, and cognitive profiles.