I have been on and off Singulair for roughly a year and half, and after reading some of these posts I have a much better understanding of where some of my feelings are coming from. When I first began taking Singulair, it really helped me breathe a lot better and I was convinced it was the best drug on earth. Slowly, over time, I began to notice that I was becoming slightly more irritable but didn't really think much of it. I got off the drug for several months because I don't enjoy being on medication. I wanted to see if a nutritional approach would help me ward off my allergies. After a few months of being off Singulair, I began to have difficulty breathing during allergy season and went back on the drug. It really helped my breathing in a big way; however, my irritability began to return. I thought I was just becoming overly stressed, but when I heard about the moodiness that can be caused by Singulair, I decided to once again get off the drug. I was off of it for several month, and have recently begun using the drug again. I haven't even made it through my first 30 days and I'm becoming a monster!! I'm yelling at my wife like crazy. I seriously felt for the first time in my life that committing suicide would be a good thing and I keep telling myself in my head how bad I suck! My temper is off the charts! I feel like I literally have no way of holding my rage back. It's like I'm an audience member to my own MMA fight. I'm absolutely getting off of this product tonight! I will keep you posted on how I feel after a couple of days not taking this drug.