Clemastine Treatment in Individuals With Williams Syndrome

Inclusion Criteria: * Individuals with Williams syndrome, which has been confirmed by genetic testing. * Ages 6-30. * Normal values in safety variables (e.g. Normal ECG 120-129/80-84). * No change in psychotropic medications and dosage during the last 4 weeks. * During the study, no pharmacological change that may impact the study (e.g. ADHD * medications). Exclusion Criteria: * Individuals with another genetic disorder besides Williams syndrome. * Individuals with Williams syndrome, younger than 6 or older than 30 years old. * Significant change in normal values in safety variables (e.g. high or low ECG). * Change in medications and dosage during the last 4 weeks prior the beginning and * during the study. * Pregnancy. * Using addictive substances such as alcohol.