Anecdata: I took Montelukast for 3 years to help with my allergies & asthma. Worked like a charm. Except for the fact that it made me really irritable. I was angry and down all the time. And I didn't really notice it until I stopped taking the tablets. That's when I started to put two and two together. I spoke to my friends about it, and they agreed that I suddenly seemed much less murdery.
Thanks for that link, I've read something about that before but haven't thought about it since I've been prescribed it myself since March.
For me since then most of the symptoms in the list on that page have actually improved. The only thing my doctor (in The Netherlands) warned me about was the bad/vivid dream part, before Montelukast I could hardly remember dreaming but now I do almost daily (but I am also sleeping much better).
That's interesting - another asthma medication I was on as a child made me an absolute horror as well - wonder if there's some relation in the mechanism of action.