Beyond Diagnostic Overshadowing: Understanding Schizophrenia in the Population with Intellectual Disability

Results

Schizophrenia is three times more prevalent in adults with ID than in the general population. This elevated prevalence may be attributed to shared genetic vulnerabilities and environmental factors, particularly obstetric complications. Accurate diagnosis of schizophrenia in individuals with ID poses significant challenges, as it requires a level of communicative ability that many lack. In those with severe or profound ID, the assessment of reality testing is often unreliable, rendering diagnosis particularly difficult. Core features such as disorganized thinking may be difficult to identify, and behaviours such as talking to oneself, interaction with inanimate objects, or abnormal postures can overlap with the behavioural phenotype of ID. Additionally, individuals with ID may experience visual rather than auditory hallucinations, potentially reflecting underlying neurobiological differences. Adults with comorbid ID and schizophrenia tend to exhibit more pronounced negative symptoms, higher rates of treatment resistance, and greater functional impairment compared to those with schizophrenia alone.