The aim of this study is to assess the suitability of selected scales (floor/ceiling effects, variability, test-retest reliability) to measure cognitive function in children with Down syndrome over 6 months, and to evaluate the influence of covariates such as age, gender or language on these neurocognitive scales.

Inclusion Criteria:

• Males and females aged 6 to 11 with diagnosis of Down syndrome (Trisomy 21). Children may have standard trisomy 21, Robertsonian translocation, isochromosome 21 (so called 21q21q Robertsonian translocation), Down syndrome with reciprocal translocation or mosaicism.
• Down syndrome children meeting clinical diagnostic criteria for generalized anxiety disorders, autism spectrum disorder, attention deficit and hyperactivity disorder, can participate in the study provided they are considered clinically stable or on stable medication for at least 8 weeks prior to the baseline visit.
• Parent or legal guardian/representative and caregiver willing to give written informed consent.
• Subjects with sufficient vision and hearing to engage in study evaluations as referred by their parents. Mild hearing loss will be allowed.

Exclusion Criteria:

• Children who may not be able to comply with the protocol or perform the outcome measures due to significant hearing or visual impairment or other issues judged relevant by the investigators
• Significant sleep disruption or moderate to severe untreated obstructive sleep apnea.
• Any condition which would make the individual or the caregiver, in the opinion of the investigator, unsuitable for the study.

Male and female children, 6 to 11 years of age inclusive, with diagnosis of Down syndrome.