I don't get how atheism is the cause. As I understand it, atheism teaches that there is no heaven waiting for the believing person, just death.
Why would you cut your life short knowing there is nothing waiting for you after you take your own life? Drugs? Mental issues?
The only exception I can understand is unbearable and untreatable pain!
Not discounting bodily pain, but more than likely also self-imposed mental anguish, a feeling of desperation and hopelessness.