My son has been taking singulair on and off since he was 11 years...

My son has been taking singulair on and off since he was 11 years old, he just had his 15th birthday. The past 2 years of his life have been filled with depression and anxiety issues. We have been to countless doctors, hospitals, therapists and now a psychologist. When he is on singulair for long periods of time he would have mood swings, depression, stomach and headache issues. I have asked the questions to all involved with him are you sure that singulair is ok to take with the depression meds? They told me yes. They recently up his dose to 10 mgs and his depression got worse! He has trouble concentrating, sleeping, and feels the world is a bad place. He is a good student, he is in sports and was popular, now he is tormented by these feelings of depression and anxiety. He has been on and off homebound instruction for the past 2 year and I have had to use family leave time from work to help him through this. My husband and I have spent a lot of hours trying to understand what has happened to our son. I have stopped giving him singulair and I hope that in the near future we can take him off his depression meds that he has been on for 1 year. How long will it take till his mind and body are rid of this drug? Why did no one tell me that this drug needs to be examined to why my son has had these very serious problem. Teenage years are hard enough with out the added conditions that my son has had to experience. I want some answers and I will give everything that I have to assure that my son will get better. Please help those who have experience what we have with the answers we are all asking.