This non-drug, longitudinal, multi-center, multi-national study will evaluate the suitability of neurocognitive tests and functioning scales for the measurement of cognitive and functioning changes in individuals with Down Syndrome. Tests will be administered at clinic visits in Weeks 1, (4) and 24. The duration of the study for each individual will be between 24 and 27 weeks.

Inclusion Criteria:

• Males and females, 12 to 30 years of age, with diagnosis of Down Syndrome
• Down Syndrome subjects meeting clinical diagnostic criteria for generalized anxiety disorders, major depressive disorders, autism spectrum disorder, attention deficit and hyperactivity disorder can participate in the study provided they are on stable medication for at least 8 weeks prior to screening and likely to cooperate and take part successfully in the study assessments

Exclusion Criteria:

• Subjects with DSM-IV axis I and II psychiatric disorders, except those authorized in the inclusion criteria
• Subjects who may not be able to comply with the protocol or perform the outcome measures due to significant hearing or visual impairment
• Subjects with evidence of dementia or meeting clinical diagnosis for dementia
• Subjects with thyroid dysfunction or diabetes that is not adequately controlled and stabilized on treatment for at least 8 weeks prior to randomization

Individuals with Down Syndrome