Psychiatric diagnoses in relation to severity of intellectual disability and challenging behaviors: a register study...

To investigate the possible association between severity of intellectual disability (ID) and presence of challenging behavior, respectively, on diagnoses of psychiatric disorders among older people with ID.

People with a diagnosis of ID in inpatient or specialist outpatient care in 2002-2012 were identified (n = 2147; 611 with mild ID, 285 with moderate ID, 255 with severe or profound ID, and 996 with other/unspecified ID). Moreover, using impairment of behavior as a proxy for challenging behavior, 627 people with, and 1514 without such behavior were identified.

Severe/profound ID was associated with lower odds of diagnoses of psychotic, affective, and anxiety disorders than was mild/moderate ID. People with moderate ID had higher odds than those with mild ID of having diagnoses of affective disorders. Diagnoses of psychotic, affective, and anxiety disorders, and dementia were more common among people with challenging behavior than among those without.

People with severe/profound ID had lower odds of receiving psychiatric diagnoses than those with mild and moderate ID. Whether this is a result of differences in prevalence of disorders or diagnostic difficulties is unknown. Further, challenging behaviors were associated with diagnoses of psychiatric disorders. However, the nature of this association remains unclear.