Relationship between psychiatric disorders and adaptive functioning in adults with intellectual disabilities

Though the very high prevalence of psychiatric disorders (PD) in people with intellectual disability (PwID), the impact of these disorders on adaptive functioning has been minimally investigated. The few contributions present in the literature focussed on children, adolescents, and individual with autism spectrum disorders (ASD). There are no studies concerning the evaluation of any kind of impact on individual skills. Comparison studies between PD and organic disorders, including neurological disorders (ND), was also underexplored. The purpose of this paper is to assess the impact of the presence of a PD on the adaptive functioning of adults with intellectual disability (ID).

In total, 107 adults with ID living in residential facilities or attending day care centers in Tuscany were consecutively assessed with the Psychiatric Instrument for the Intellectually Disabled Adult (SPAID-G), the Diagnostic Manual-Intellectual Disability (DM-ID) criteria, and the Vineland Adaptive Behavior Scales (VABS). The scores were statistically compared and results were controlled for level of ID and other background variables.

The presence of a PD resulted to have a significant negative impact on individual adaptive skills. Participants with PD scored significantly lower than those without PD in communication and socialization areas of VABS. Participants with ND scored significantly lower than people without ND in daily living and motor skills. The average scores of participants with only PD and those of participants with PD and ND showed no significant differences. Significant differences were found between participants with only ND and participants with ND and PD in the interpersonal relationship subscale.

As far as the best knowledge, this is the first study on the evaluation of the impact of any kind of PD on the abilities of PwID. This paper suggests that the presence of a PD seems to have a relevant negative impact on functioning of PwID higher than that of ND, particularly in communication and socialization skills.