Diagnosing intellectual disability in a forensic sample: Gender and age effects on the relationship between cognitive and adaptive functioning

Background The relationship between adaptive behaviour and cognitive functioning in offenders with intellectual disabilities is not well researched. This study aims to examine gender and age effects on the relationship between these two areas of functioning.Method The Vineland Adaptive Behavior Scales (VABS) and the Kaufman Brief Intelligence Test (K‐BIT) were administered to 202 volunteer participants accused or convicted of crimes, 9% being of Australian indigenous background. The sample included males and females, juveniles and adults.Results Significant correlations were found between all subtests and domains on each instrument; for males under 18 years, correlations were lower, and significant correlations were absent between K‐BIT Vocabulary and VABS subdomains and composite standard score for this group.Conclusions Generally there is convergence between assessment of adaptive behaviour and cognitive skills, across age ranges and for both genders. Caution is needed in interpreting test results for young male offenders with possible intellectual disability; repeat assessments are advisable for this group.