UPDATE:It is now a week since my 6 yr old son stopped taking sing...

i am so happy your son is doing better. i made the connection back in march 2007. my son was also 6 yrs old. he had been on singulair for 3 yrs. he made an amazing recover after 3 weeks. he had suffered from anxiety, fear, irritability, self doubt, nightmares, stomach pains, leg pains, occasional weird vomiting episodes, just to name a few. during the final months, he was on the higher dosage of 5mg. at the higher dosage, he also suffered a facial tic, dilated pupils and hallucinations. i finally made the connection. his recovery was amazing. within 3 weeks, he was a different child. merck/singulair took 3 years of his childhood. shame on them !!!