Effect of Specialized Psychiatric Assessment and Precision Diagnosis On Pharmacotherapy in Adults with Intellectual Disability

Background/Objectives: Adults with intellectual disability (ID) experience high rates of psychiatric comorbidity but often face diagnostic challenges and treatment barriers, often leading to inappropriate psychotropic medication use. This study examined the extent to which specialised psychiatric assessment and improved diagnostic accuracy had an im-pact on medication management and clinical outcomes in adults with ID and co-occurring psychiatric disorders. Methods: This observational retrospective study ana-lysed medical records from 25 adults with ID who underwent specialised psychiatric as-sessment at a community-based service in Italy between January 2023 and January 2024. Psychopathological diagnoses were established according to Diagnostic Manu-al-Intellectual Disability 2nd version (DM-ID2) criteria, based on clinical observation and a comprehensive assessment using validated instruments. Clinical outcomes were as-sessed using a psychometric tool encompassing multiple psychopathological and behav-ioral dimensions. Data on psychotropic prescriptions and side effects were also collected. Non-parametric analyses were performed, with significance set at α=0.05. Results: The proportion of patients with a psychiatric diagnosis increased from 32% to 96% after spe-cialized assessment (p< 0.001), with notable rises in depressive (0% to 32%), bipolar (8% to 36%), anxiety (4% to 24%), and impulse control disorders (0% to 16%). First-generation an-tipsychotic prescriptions decreased (from 36% to 8%, p=0.023), while antidepressant use increased (from 12% to 52%, p=0.004). The mean number of side effects per patient de-clined from 1.6 to 0.5 (p< 0.001), particularly the elevated prolactin level, and psychomotor retardation. Significant improvements were observed in symptom intensity and frequency across multiple domains, including aggression, mood disturbances, and compulsions (p< 0.001). Conclusions: Specialised psychiatric assessment substantially improved diag-nostic accuracy, medication management, and clinical outcomes in adults with ID. The increase in psychiatric diagnoses reflects improved identification, addressing key chal-lenges in precision diagnosis for people with neurodevelopmental disorders. Evi-dence-based medication optimisation reduced inappropriate antipsychotic use and side effects. These findings support the need for specialised assessment and precision diagnosis to improve psycho-pharmacological interventions and outcomes for this vulnerable population.