gens). Perinatal causes include a variety of labor and delivery-related events leading to
neonatal encephalopathy. Postnatal causes include hypoxic ischemic injury, traumatic
brain injury, infections, demyelinating disorder s, seizure disorders (e .g., infantile spasms),
severe and chronic social deprivation, and toxic metabolic syndromes and intoxications
(e.g., lead, mercury).
Culture-Related Diagnostic Issues 
Intellectual disability occurs in all races and cultures. Cultural sen sitivity and knowledge
are needed during assessment, and the individu al’s ethnic, cultural, and linguistic back-
ground, available experiences, and adaptive functioning within his or her community and
cultural setting must be taken into account.
Gender-Related Diagnostic Issues
Overall, males are more likely than female s to be diagnosed with both mild (average
male:female ratio 1.6:1) and severe (average male:female ratio 1.2:1) forms of intellectual
disability. However, gender ratios vary widely  in reported studies.  Sex-linked genetic fac-
tors and male vulnerability to brain insult ma y account for some of the gender differences.
Diagnostic Markers
A comprehensive evaluation includes an assess ment of intellectual capacity and adaptive
functioning; identification of  genetic and nongenetic etiolo gies; evaluation for associated
medical conditions (e.g., cerebral palsy, seiz ure disorder); and eval uation for co-occurring
mental, emotional, and behavior al disorders. Components of the evaluation may include
basic pre- and perinatal medical history, three- generational family pedigree, physical exam-
ination, genetic evaluation (e.g., karyotype or  chromosomal microarray  analysis and testing
for specific genetic syndromes), and metabo lic screening and neuroimaging assessment.
Differential Diagnosis