The term dual diagnosis can refer to the co-occurrence of an intellectual disability and a mental disorder. While such a term may have some advocacy rationale aimed at facilitating improved mental health care for those with intellectual disabilities, it is proposed that the construct has flawed underpinnings, and its application may problematize mental health service delivery. A core concern is the promotion of categorical diagnostic models, whereas dimensional models may more accurately reflect underlying continuums for both cognitive and mental health challenges. A categorical diagnostic approach may also contribute to questionable dichotomization of mental health difficulties in persons with intellectual disabilities into “problem or challenging behaviours” versus “mental disorders.” Organizing services based on beliefs that such distinctions and categorical classifications are accurate may contribute to unnecessary and inappropriate fractionation of interventions and create additional service barriers for a vulnerable population. It is proposed that the term dual diagnosis be abandoned and replaced by systematic use of a dimensional approach to help facilitate assessment, intervention evaluation, and equitable service access.
John D. McLennan, MD, MPH, PhD
The Canadian Journal of Psychiatry, Vol 63, Issue 9, 2018