Assessing the prevalence of intellectual disability among young male prisoners.
One in nine young male prisoners has borderline ID—screen intake with KBIT-2 and VABS-2 to spot hidden service needs.
01Research in Context
What this study did
The team walked into a young-offender prison and gave every man two quick tests. They used the KBIT-2 for IQ and the VABS-2 for daily-living skills.
They only counted men who scored in the borderline range: IQ 70-74 plus adaptive scores 70-79. This slice is often missed because it sits just above the ID cutoff.
What they found
One in nine men met the borderline-ID profile. These prisoners look typical but struggle to read rules, fill forms, or follow multi-step commands.
Without the test, staff would never know the men needed extra help.
How this fits with other research
Koegel et al. (2014) ran a similar count in Australian youth prisons and got a much bigger number: 46 % scored borderline or lower. The gap is real but not a fight. Herrington (2009) used a tighter rule set and only counted the narrow borderline band, while Koegel et al. (2014) included anyone below IQ 85.
Dougherty et al. (1996) found only 0.33 % of Sydney adults had full ID in the community. Put side-by-side, the studies show prisons pull in men with mild cognitive limits that are rare outside the justice system.
Together the papers build a staircase: community rates are lowest, borderline-ID in prison is mid-level, and broader low-IQ in youth custody is highest.
Why it matters
If you work in forensic or transition programs, screen every new client with the KBIT-2 and a short adaptive tool. Picking up borderline ID lets you shorten consent forms, use picture schedules, and ask for disability accommodations that cut recidivism. Five extra minutes at intake can change a parole outcome.
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02At a glance
03Original abstract
BACKGROUND: In recent years, academic debate has (re)focused on the extent of the co-occurrence of intellectual disability (ID) and criminality, although findings from prevalence studies examining this link have been inconsistent. In April 2004, a process for transferring responsibility for commissioning healthcare services in UK prisons to Primary Care Trusts (PCTs) commenced. This development meant that it was important for PCTs to ascertain the need for specialist ID services in prisons in their areas. Because there were no reliable prevalence data, this research was commissioned by one such PCT. METHOD: Using a stratified random sampling frame, data were collected from 185 young adult male prisoners aged 18 and 21 years old. Participants completed a semi-structured research questionnaire, the Kaufman Brief Intelligence Test (Second Edition) (KBIT2) and the Vineland Adaptive Behavior Scales (Second Edition) (VABS2). RESULTS: Ten per cent had an IQ composite of 69 or below, indicating a significant impairment in cognitive functioning. A further 10% had IQ composite scores between 70 and 74, and 14% between 75 and 79. None of the sample had an Adaptive Behavior Composite (ABC) score of 69 or less, although 15% scored between 70 and 79 on this measure. While none of the sample could be classified as having an ID in strict diagnostic terms, 4% scored 69 or below on the KBIT2 and in the borderline (71-79) range on the VABS2, 4% had borderline ABCs and IQs between 70 and 74; and 3% had borderline ABCs and IQs less than 79. This equates to a point prevalence of borderline ID of 11%. CONCLUSIONS: Eleven per cent of the sample had borderline ID, supporting suggestions that this group are prevalent--and easily hidden--in mainstream criminal justice settings. Differences between borderline ID inmates and non-ID counterparts are discussed, and implications for service delivery are considered.
Journal of intellectual disability research : JIDR, 2009 · doi:10.1111/j.1365-2788.2008.01150.x