To evaluate the suitability (i.e. number of tests completed and number of participants completing the tests, variance estimate of baseline and of the change from baseline values) of neurocognitive tests and functioning scales in view of their use in future multicenter, multinational clinical efficacy trials testing a putative cognitive enhancer for individuals with Down syndrome aged 6-30.

Inclusion Criteria:

• Subjects may have standard trisomy 21, Robertsonian translocation, isochromosome21,Down syndrome with reciprocal translocation or mosaicism.
• Availability of parent or other reliable caregiver who agrees to accompany the subject to clinic visits, provide information about the subject's behavior and symptoms.
• Down Syndrome subjects meeting clinical diagnostic criteria for generalized anxiety disorders, major depressive disorders, autism spectrum disorder, attention deficit and hyperactivity disorder, can participate to the study provided they are on stable medication for at least 8 weeks prior to screening.

Exclusion Criteria:

Individuals 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.

People with Down syndrome