The development of a new measure for the assessment of psychopathology in adults with intellectual disability.

BACKGROUND: People with intellectual disability (ID) and untreated psychiatric disorder lead unnecessarily difficult and unhappy lives. The prevalence of mental illness in children and adults with ID is greater than that found in the general population. A carer-completed checklist of psychopathology that could be used with both children and adults would help identify those individuals with ID most likely to have a mental health problem, help ensure that they receive the limited services that are usually available and also assist the process of clinical assessment, diagnosis and management.
METHOD: This research aimed to develop a reliable and valid carer-completed checklist of psychopathology for adults with ID by redeveloping an existing measure for children with ID, the Developmental Behaviour Checklist (DBC-P). The new checklist, The Developmental Behaviour Checklist for Adults (DBC-A) was devised by changing, deleting and adding to DBC-P items. Reliability studies were conducted with paid and family carers, and DBC-A scores were compared with the results from two other measures of psychopathology.
RESULTS: One DBC-P item was deleted, seven items changed and 12 items added. The psychometric properties of this new checklist, the DBC for Adults with ID (DBC-A), were investigated and found to be satisfactory. Intraclass correlations for test-retest and inter-rater reliability ranged from 0.72 to 0.85, and concurrent validity with two measures of emotional and behavioural disturbance was satisfactory.
CONCLUSIONS: The carer-completed DBC-A provides a broad and comprehensive survey of the emotional and behavioural problems of adults with ID. It has satisfactory psychometric properties and therefore can be used with confidence in clinical, research and service settings, and its development allows continuous assessment of psychopathology across the lifespan for all people with ID.