If you take the allergy and asthma medication Singulair (which I do, by the way), you'll want to know that the FDA is investigating its link to depression and suicidal tendencies. Used by both children and adults, possible side effects can also include tremors and anxiety. It's been reported that at least three people who were taking Singulair have committed suicide.
Neither the FDA nor Merck (the makers of this drug) recommend that you stop taking it, unless you have noticed severe mood changes or other symptoms. Talk to your doctor if you have any concerns.
If you want to see a video with more information then