The quoted prevalence of intellectual disability (ID) among adults with psychiatric illness varies widely. Some believe that these people are protected from certain intellectual and psychological stress by having ID, and therefore, are less prone to develop psychiatric illness. However, in the past decades, the more prevailing view is that people with ID are more vulnerable to psychosocial stress than people without ID, and therefore, are more likely to develop psychiatric symptomatology. According to various population surveys the probability of suffering a mental disability increase with age. Delusional disorder is as well a disease related to advanced stages of life.

The aims of the present study is to establish the prevalence of functional intellectual disability among adults who fulfil DSM 5 delusional disorder criteria.

Our data come from a case register study of delusional disorder in Andalucia (Spanish largest region). By accessing digital health data, we selected 1927 cases, which meet criteria DSM 5 for delusional disorder collecting whether in its history intellectual disability was registered by the referent psychiatrist.

Of our sample, 2.6% had reflected some kind of intellectual disability in their digital clinical record.

These percentage has been found to concur with other epidemiological studies linking mental retardation and psychotic spectrum disease although there are no epidemiological data published to the best of our knowledge that correlate delusional disorder specifically and intellectual disability.

The authors have not supplied their declaration of competing interest.