Intellectual disability and dementia are age-dependent terms for a cognitive impair occurring during
developmental age and in adulthood, respectively. Intellectually disabled people like any other people
may develop dementia in adulthood. Thus, clinicians should learn to differentiate dementia-indicating
signs from intellectual disability related cognitive deficiencies for an early diagnosis and treatment
onwards. In intellectual disability, intellectual and adaptive skills of an individual are two standard
deviations below the expected age-matched population, and dementia is characterized by a progressive
cognitive decline. The cause of both disorders can be genetic, acquired or multifactorial. An increased
risk of Alzheimer's disease in Down syndrome is well known unlike the development of dementia in
other intellectual disability syndromes. This commentary discusses 1) how the dementia indicating
signs present in intellectually disabled persons, 2) why it is important to distinguish dementia (and
its causes) from intellectual disability and 3) why it is important to know the etiology of intellectual
disability.
