The main limitation in the present study is the fact that it included no control subjects. Nevertheless, the research group will take this issue into consideration in future studies. Additionally, this study was conducted on DS children attending special needs schools. Also, it should be noted that majority of DS children in Yemen still reside at home with no educational or vocational plan from parents or guardians as they are often stigmatized by the society. Therefore, generalization must be made carefully as this study population may not reflect the DS population in Yemen.