I have been on singulair for almost 2 years and i feel that it helps a lot actually when i don't have it my asthma acts up a lot, but it's only mild asthma so it's not too bad but it makes the difference. occasionally get a headache possibly attributed to it or more likely the zrytech however you spell that, but i like the singulair better than anything else and have had no thoughts of suicide or moodiness or anything weird.