Psychopathology in borderline intellectual functioning: a narrative review

Studies on psychiatric comorbidity in individuals with borderline intellectual functioning (BIF) are scarce, particularly with respect to certain diseases frequently observed in clinical practice. The purpose of this paper is to discuss the relevance of epidemiological research to psychiatric comorbidity in people with BIF.

Systematic searches of MEDLINE, EMBASE and Cochrane databases. Inclusion criteria: publications about BIF appearing between 1995 and 2017; epidemiological findings about comorbid mental disorders in individuals with BIF; and studies comparing BIF, mild intellectual disability (ID) and normal intellectual functioning. The discussion covers 24 of the 224 studies initially considered.

The most frequent psychiatric comorbidity reported was personality, post-traumatic as well as psychotic disorders, followed by psychosis, attention deficit and hyperactivity disorder, bipolar and sleep disorders. Individuals with BIF exhibit psychiatric comorbidity more frequently than individuals with normal intellectual functioning. Some psychiatric comorbidities were similarly prevalent in patients with BIF and those with mild or moderate ID; however, the prevalence was always higher in people with severe ID. Environmental factors, especially psychosocial adversity, seem to play an important mediating role. Pharmacotherapy is the most common treatment approach, including behavioural disorders.

This review of literature on mental disorders in people with BIF demonstrates the epidemiological relevance of psychiatric comorbidity, especially personality and post-traumatic disorders. Mental health professionals, general practitioners and other workers in outpatient settings have to be aware about the vulnerability and even fragility of people with BIF.