Aiden is a 24-year-old man with autism and moderate intellectual disability (ID) admitted to the psychiatric unit after a sudden worsening of anxiety and behavior. He’s always had trouble with loud noises and other sensory experiences, but things escalated recently after he witnessed a serious car accident. He’s been pacing constantly, crying for hours, biting his nails until they bleed, and hitting his head hard enough to cause bruises. He’s also been refusing most meals. His medical history includes mitral valve prolapse, and his family history includes a maternal uncle and cousin with ID and autism. Aiden has never had genetic testing.

After encountering a case like Aiden’s, you might wonder whether a genetic condition could be contributing to his presentation. Many genetic neurodevelopmental disorders are identified in childhood, but not all. Some patients reach adulthood undiagnosed, particularly if earlier evaluations were limited or never pursued. In fact, if you test patients with autism, intellectual disability, or developmental delay, nearly one in five will have an identifiable underlying genetic cause (Muhle RA et al, J Am Acad Child Adolesc Psychiatry 2017;56(11):910–913). Identifying that cause can reshape your treatment plan, flag medical issues that need monitoring, and prompt evaluation of at-risk relatives.

When to suspect a genetic condition
A few red flags should prompt a deeper look. Autism, ID, or global developmental delay are the most common clues. Dysmorphic features or congenital anomalies, like atypical facial traits and cardiac or renal defects, add to the suspicion. A family history of ID or autism in multiple relatives is another strong signal. Repetitive or stereotyped behaviors like hand-flapping or rocking may point to specific syndromes, and new-onset cognitive or functional decline in adolescence or early adulthood can indicate a previously unapparent genetic condition.

Aiden has autism and ID—that’s your first clue. He also has mitral valve prolapse, which is a known feature of fragile X syndrome. And his maternal uncle and cousin both have ID and autism, suggesting an X-linked inheritance pattern. These details together should put Fragile X near the top of your differential.

Syndromes psychiatrists are most likely to encounter

22q11.2 deletion syndrome (DiGeorge syndrome)
This is one of the most underrecognized genetic conditions in adult psychiatry. Up to 30% of individuals with this deletion develop psychosis, often resembling schizophrenia—making it one of the strongest known genetic risk factors for psychotic illness (Schneider M et al, Mol Psychiatry 2014;19(11):1205–1211). If you have a patient with treatment-resistant psychosis who also had a cleft palate repair as a child or a history of congenital heart disease (especially tetralogy of Fallot), think 22q11.2. Other clues include a history of hypocalcemia, immune deficiency, and subtle facial features like hooded eyelids or small ears. Anxiety and ADHD are also common. The deletion is found in roughly 1 in 4,000 live births, so it’s not as rare as it sounds.

Fragile X syndrome
Fragile X is the most common inherited cause of intellectual disability, and it’s the condition most relevant to Aiden’s case. Males typically present with moderate to severe ID, autism (in 25%–50% of cases), ADHD, anxiety, and stereotypies like hand-flapping. The physical exam may show a long face and prominent ears. Post-pubertal males may also have macroorchidism (enlarged testes). Mitral valve prolapse and joint laxity are also common. An important detail for family counseling: Female carriers of the premutation may have milder symptoms like anxiety, attention problems, or learning difficulties, and they are at risk for fragile X–associated primary ovarian insufficiency (Hagerman RJ et al, Curr Pediatr Rev 2008;4(1):40–52).

Prader-Willi syndrome You’re most likely to encounter Prader-Willi in the context of behavioral crises. Patients typically have mild to moderate ID, and the syndrome’s hallmark is hyperphagia—an insatiable drive to eat that emerges in childhood and leads to severe obesity if food access isn’t carefully managed. Psychiatrically, you’ll see compulsivity (skin picking, hoarding), emotional dysregulation with intense tantrums, anxiety, depression, and in some cases psychosis. Excessive daytime sleepiness is also common. The behavioral profile is distinctive enough that if a patient with ID presents with both compulsive eating behaviors and skin-picking, Prader-Willi should be on your list.

Less commonly seen by psychiatrists
Several other genetic syndromes have psychiatric features but are generally diagnosed in childhood and managed primarily by other specialties. You’re unlikely to be the first to identify these, but you may see these patients for comorbid psychiatric care. For a quick guide to key features, see the “Genetic Syndromes Relevant to Psychiatric Practice” table below. For a detailed supplement with resources, see:.

From the Clinical Update
“Genetic Conditions With Psychiatric Manifestations”
By Courtney S. Roberts, MD and Victoria Hendrick, MD
The Carlat Hospital Psychiatry Report
Volume 6, numbers 3 and 4
April/May/June 2026

Understanding genetic testing
Genetic testing in this context isn’t a single test. Instead, think of it as a toolkit with different levels of resolution. Chromosomal microarray (CMA) is the workhorse. It scans the genome for missing or extra segments of DNA and catches most of the deletions and duplications behind these syndromes. Fragile X testing is a separate, targeted test because the specific trinucleotide repeat expansion that causes fragile X doesn’t show up on CMA. Karyotyping is an older test that examines whole chromosomes under a microscope; it’s useful when you suspect something like Down syndrome or Turner syndrome, but it misses the smaller changes CMA can detect.

For most patients with unexplained ID or autism who haven’t been tested, start with CMA plus fragile X testing. The American Academy of Pediatrics recommends this combination as the first-tier workup, and the same logic applies in adults who were never evaluated (Schaefer GB and Mendelsohn NJ, Genet Med 2013;15(5):399–407). If physical features point toward a specific whole-chromosome condition (eg, suspected Down or Turner syndrome), add karyotyping. If first-tier testing is negative but your clinical suspicion remains high, refer to a geneticist. More comprehensive sequencing tests that analyze many genes at once may be the next step. Coordinate the workup with a genetic counselor to ensure appropriate pre- and post-test counseling and interpretation of results.

Practical considerations
Insurance generally covers CMA and fragile X testing when the patient has documented developmental delays, autism, or ID. Preauthorization requirements vary by plan, so check before ordering. Out of pocket, CMA typically runs $500–$1,500, while fragile X testing is in the range of $300–$500. Results usually take two to four weeks. If testing can’t be completed during an inpatient stay, initiate an outpatient referral. Don’t let the logistics of hospitalization become a reason to skip it. You can help connect patients and families with genetic counselors through the National Society of Genetic Counselors at.

Genetic testing can bring enormous relief to families who have struggled for years without answers, and a clear diagnosis often reduces guilt or self-blame. But testing can also uncover incidental findings—like a predisposition to BRCA-associated cancers—that raise new anxieties. Discuss these possibilities with patients and families before ordering tests so they’re prepared for unexpected results.

Treatment approaches
You can manage most psychiatric symptoms in these patients with a combination of medications and behavioral supports, guided by the patient’s specific symptoms, functional level, and medical comorbidities. SSRIs are typically first line for anxiety or obsessive-compulsive symptoms. Start at low doses (eg, escitalopram 5 mg, sertraline 25 mg). For acute anxiety or agitation, hydroxyzine 25–50 mg as needed is a reasonable option. For irritability or aggression, aripiprazole (starting at 2 mg) or risperidone (starting at 0.5–1 mg) are both FDA approved for irritability in autism. The general rule is to start low and go slow, as these patients are often more sensitive to side effects (for more treatment approaches, see:).

Establishing a genetic diagnosis does not usually change day-to-day psychiatric management. Treatment remains symptom-based: Anxiety is treated as anxiety, psychosis as psychosis, irritability as irritability. The value of identifying the genetic condition is that it can guide medical monitoring, clarify prognosis, reduce family uncertainty, and prompt testing of at-risk relatives. A diagnosis may also help clinicians anticipate vulnerabilities (eg, higher psychosis risk in 22q11.2 deletion) or medication sensitivities.

Behavioral strategies
In inpatient psychiatry, behavioral interventions are often the most effective tools for stabilization. Prioritize structure and predictability: Maintain consistent routines, use visual schedules, and minimize unstructured time. Identify sensory triggers (noise, lighting, crowding) and modify the environment as needed. Quiet spaces, reduced stimulation, or sensory supports (eg, weighted blankets, fidget tools) can significantly reduce agitation.

Use a functional approach to behavior. Try to figure out what the patient’s behavior accomplishes—escape, attention, sensory input, or access to preferred items—and intervene at that level. Teach and reinforce replacement behaviors (eg, using a “break” request instead of self-injury). Keep communication simple and concrete, and rely heavily on positive reinforcement. For syndrome-specific risks (eg, food seeking in Prader-Willi), restrict unsupervised food access, use locked storage, schedule structured meals, and maintain consistent staff limit-setting.

During Aiden’s hospitalization, you start escitalopram 5 mg daily for his anxiety and hydroxyzine 25 mg as needed for agitation. Structured routines and sensory supports reduce his pacing and self-injury. CMA and fragile X testing confirm fragile X syndrome. You discuss the diagnosis with his mother, explain the X-linked inheritance pattern, and recommend genetic counseling and testing for female relatives who may be carriers. The social worker connects the family with the National Fragile X Foundation and arranges in-home supportive services. You schedule follow-up with a clinical geneticist for long-term cardiac surveillance of Aiden’s mitral valve prolapse.

Carlat Verdict: We often care for patients with developmental disorders, but it’s easy to miss an underlying genetic diagnosis, especially in adults who weren’t tested as children. Subtle physical features, family history patterns, or distinctive behaviors may point to a genetic syndrome. While establishing a diagnosis may not dramatically change immediate psychiatric treatment, it can clarify medical monitoring needs, guide family counseling, and anticipate long-term risks. If the picture seems suggestive, start with CMA and fragile X testing. Genetic counselors can help families navigate the diagnosis and coordinate ongoing care.