Psychiatric diagnostic dilemmas among people with intellectual and developmental disabilities

Research regarding the accuracy of co-morbid psychiatric diagnoses in individuals with intellectual and developmental disabilities (IDD) is sparse. Yet correct diagnostic assignment is vital so that effective and appropriate treatment can be implemented, especially for the large numbers of individuals requiring expensive and restrictive behavioural health crisis services.

A retrospective review of de-identified data from multidisciplinary specialty team assessments completed for 50 individuals with ID (IntellectualDisability) with and without ASD and unresolved behavioural health challenges was conducted. The accuracy and reliability of the psychiatric diagnoses upon referral were compared with the diagnoses after the comprehensive team evaluation, and within-individual diagnostic agreement was calculated. The agreement between the Mood and Anxiety Semi-Structured interview tool (MASS) and the full team evaluation was also calculated. The influence of demographic and clinical characteristics on diagnostic agreement was explored.

The most common chief complaints upon referral were aggression to others and self-injurious behaviour. Individuals were taking a median of six medications (interquartile range: 5 to 7); 80% were taking an antipsychotic medication. The most common medical conditions were constipation (70%) and gastroesophageal reflux disease (52%). Measures of interrater reliability of the referral diagnoses with the team assessment were below 0.5 (kappa range: -0.04 to 0.39), with the exception of ruling out dementia (kappa = 0.85). The interrater reliability estimates for the MASS evaluations for depression and anxiety were higher (kappa = 0.69 and 0.64) and reflected higher sensitivity and PPV. The odds of any referral diagnosis being confirmed by team evaluation were low: 0.25 (range: 0 to 0.67). The level of diagnostic agreement for each patient was not significantly attributable to demographic or clinical characteristics, although effect sizes indicate a possible positive relationship to age and the number of prescribed psychotropic medications at referral.

Individuals in the current study had serious psychiatric and behavioural problems despite psychiatric care in their communities. The majority of psychiatric diagnoses provided upon referral were not supported by the multidisciplinary specialty team's assessment. In addition to possible diagnostic inaccuracy, the group in the study suffered from multiple medical co-morbidities and were exposed to polypharmacy. Results emphasise the importance of multidisciplinary evaluation by clinicians with expertise in neurodevelopmental disabilities when people with ID with and without ASD have complex behavioural health needs that are unresponsive to usual care. In addition, based on agreement with the full team evaluation, the MASS shows promise as an assessment tool, especially with regards to identifying anxiety and depression.