Mental Retardation

      According to the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV), Mental retardation (MR) is characterized “by significantly subaverage intellectual functioning (an IQ of approximately 70 or below) with onset before age 18 years and concurrent deficits or impairments in adaptive functioning” (American Psychiatric Association, 1994, p. 37). Subcategories differentiated by IQ scores include (DSM-IV, p. 40)

·     317    Mild MR

IQ Level 50-55 to approximately 70

·     318.0 Moderate Retardation

IQ Level 35-40 to 50-55

·     318.1 Severe MR

IQ Level 20-25 to 35-40

·     318.2 Profound MR

IQ Level Below 20 or 25

·     319    MR, Severity Unspecified


The dividing line between categories is given as a range because IQ scores may involve a measurement error of approximately 5 points. IQ scores are supposed to be unaffected by culture or language, but this assumption has been challenged (Beiser & Gotowiec, 2000). The most common “predisposing factor” for mental retardation is “Early alterations of embryonic development,” which accounts for about 30% of the cases of MR. This factor includes “prenatal damage due to toxins (e.g., maternal alcohol consumption…).” Thus, prenatal alcohol exposure is recognized as one of the major predisposing factors in MR.

      “Borderline Intellectual Functioning” (DSM-IV Code V62.89) describes an IQ range that is higher than that for Mental Retardation (generally 71-84). Because of the measurement error, the DSM-IV observes that “Differentiating Mild Mental Retardation from Borderline Intellectual Functioning requires careful consideration of all available information” (p.45), and “is especially difficult when the coexistence of certain mental disorders (e.g., schizophrenia) is involved” (p. 684). It may therefore be the case that FAS/ARND is one of those mental disorders that makes such differentiating difficult.

      FAS is the leading known cause of mental retardation, surpassing both Spina Bifida and Down’s Syndrome ([Streissguth, Aase, Clarren, Randels, LaDue, & Smith[RMS1] ], 1991; Cook, et. al., 1990, p. 17). However, in a large clinical sample, only 27% of FAS patients and 9% of “FAE” patients had an IQ of 70 or less (Streissguth, Barr, Kogan & Bookstein, 1996, 20). Other studies include:

·     A study of 145 FAS/ARND cases in Alaska (Colberg, 1997) showed that 20% had learning disability or mental retardation.  Most of these 145 cases (83%) were Alaska Natives.  Multiple disabilities were common.

·     In another study in Alaska of 36 children with FAS, 20% had mental retardation (Gessner, Bischoff, Perham-Hester, Chandler, & Middaugh, 1998).


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