Borderline intellectual functioning is included in the DSM-5 as one of many V codes, or “other conditions that may be the focus of clinical attention” (APA, 2013). In the DSM-IV this condition was defined as having an IQ falling within the range of seventy-one to eighty-four. The DSM-5 does not specify an IQ range, but states that it is important to differentiate borderline intellectual functioning from mild intellectual developmental disorder based on “careful assessment of intellectual and adaptive functioning and their discrepancies” (APA, 2013).
Below average cognition—that is, cognition falling within the range warranting the designation of borderline intellectual functioning—is relatively common among clients with a broad range of difficulties seen by counselors (Koenen et al., 2009). Despite its fairly high prevalence in clinical practice, it can be difficult to reliably identify borderline intellectual functioning particularly among adults who may “age out” of some of the more obvious manifestations of this condition and/or appear to possess adequate verbal and social interaction skills. Such a clinical presentation frequently results in an overestimation of general level of cognitive/intellectual and adaptive functioning.
Individuals with borderline intellectual functioning have early-onset problems with academic learning and many have associated difficulties with attention, concentration, social interaction, and effective coping. Consequently, this condition is frequently confused with neurodevelopmental disorders, in particular attention deficit disorder, autism spectrum disorder (mild severity), and specific learning disorder.
The DSM-5 diagnosis of specific learning disorder does not require the results of IQ testing although criterion B stipulates confirmation of this diagnosis by formal psychoeducational assessment. This type of evaluation often, but not always, involves completion of a standardized test of intelligence. Yet, many persons diagnosed with specific learning disorder—especially those at the moderate and severe levels of impairment as defined in DSM-5—have IQs that fall within the range warranting the designation of borderline intellectual functioning.
Additionally, lower general intellectual functioning is a significant risk factor for the development of psychiatric disorders (Wieland, Kapitein-de Haan, & Zitman, 2014). Borderline intellectual functioning is also a significant risk factor for treatment noncompliance and poor treatment outcome due to persistent problems with attention, concentration, memory, comprehension, reasoning, and problem solving. As well, it is a good predictor of adverse psychosocial consequences, notably limited academic and vocational achievement, chronically low self-esteem, personality difficulties, and recurrent adjustment problems (Peltopuro, Ahonen, Kaartinen, Seppälä, & Närhi, 2014; Wieland, Van Den Brink, & Zitman, 2015).
Individuals with borderline intellectual functioning are also vulnerable to diagnostic overshadowing. This is a common error in clinical judgment whereby established medical and/or mental health diagnoses serve to obscure other important aspects of a client’s clinical status, including significant difficulties with cognitive/information processing, that can contribute to the development and persistence of psychiatric symptoms.
For all of these reasons, it is important to reliably identify this condition to facilitate optimal intervention. The following indicators strongly raise the index of suspicion for borderline intellectual functioning:
- “Across the board” difficulties with the acquisition of academic skills evident by the early elementary school years
- History of psychoeducational assessment and/or special education for presumptive attentional, learning, and/or other neurodevelopmental difficulties
- Deficits in social competence and/or judgment
- Limited formal schooling and vocational attainment which are not well explained by sociocultural factors, a trauma history, one or more neurodevelopmental disorders and/or major mental illness
Review of educational and psychoeducational records and a client’s mental health history, together with updated psychological and neuropsychological testing is the most reliable way to determine if a client warrants the designation of borderline intellectual functioning. Testing should involve administration of a gold standard test of global cognitive/intellectual functioning— Wechsler Adult Intelligence Scale- IV (WAIS-IV), the Stanford-Binet-5, or the Woodcock-Johnson Test of Cognitive Abilities-IV—as well as a gold standard measure of adaptive functioning such as the Adaptive Behavior Assessment System-3 or the Vineland Adaptive Behavior Scales-II.
American Psychiatric Association (APA). (2013). Diagnostic and statistical manual of mental disorders (5th ed.). Washington, DC: Author.
Koenen, K. C., Moffitt, T. E., Roberts, A. L., Martin, L. T., Kubzansky, L., Harrington, H., . . . Caspi, A. (2009). Childhood IQ and adult mental disorders: A test of the cognitive reserve hypothesis. American Journal of Psychiatry, 166(1), 50–7.
Peltopuro, M., Ahonen, T., Kaartinen, J., Seppälä, H., & Närhi, V. (2014). Borderline intellectual functioning: A systematic literature review. Intellectual and Developmental Disabilities, 52(6), 419–43.
Wieland, J., Kapitein-de Haan, S., & Zitman, F. G. (2014). Psychiatric disorders in outpatients with borderline intellectual functioning: Comparison with both outpatients from regular mental health care and outpatients with mild intellectual disabilities. Canadian Journal of Psychiatry, 59(4), 213–9.
Wieland, J., Van Den Brink, A., & Zitman, F. G. (2015). The prevalence of personality disorders in psychiatric outpatients with borderline intellectual functioning: Comparison with outpatients from regular mental health care and outpatients with mild intellectual disabilities. Nordic Journal of Psychiatry, 69(8), 599–604.