Many mysteries symptoms and conditions

Be very wary of this drug! My son was on it for a year and a half ...the last six months were a veritable nightmare for him. Severe anxiety issues (had to be hospitalized at one point ) and depression. Doctors kept saying it was not the medication but when I googled the drug side effects and stumbled on a blog about singulair problems , I told my son and off the medication he went. Within a month he was back to his normal self .
Thank goodness he was old enough to tell me how he was feeling ( 17 years old at the time) but what about very young children on this drug...how can they voice their problems when they don't have the vocabulary or knowledge of what is "normal"?