In light of this, perhaps the better question is "What sins cause a person to lose their salvation?" God tells us in His word that those who stray from Him will encounter the disciplinary hand of God - Hebrews 12:4-11; all for the purpose of bringing a straying sinner back into fellowship with Himself. He refuses to sit by as we stray away from Him. We are told a number of times that God will even go so far as to take a person home to heaven in discipline - 1 Corinthians 11:30-32. Verse 32 indicates that before we would ever lose His grace, He will take our lives. This is consistent with those passages where Christ tells us that "all that come to Me I will not cast out." - John 6:37. We are secure precisely because our salvation is the work of God - not ourselves. In the same way, our sanctification is the work of God - we yield ourselves to Him and He perfects us through His grace. In regard to this, someone once said: "If your faith fizzles before the finish, it was faulty from the beginning!"
So, we believe that you cannot lose your salvation - it was the work to God that He said that he would perform to the end.
Now, there are rare times when a Christian will suffer from some disorder that causes their chemical balances to be altered and they suffer from severe depression. In such occasions, some believers have killed themselves - and they did not go to Hell. But, these are to exception to the norm. Always remember that Christ said that he came that we might have joy. A person who believes their life to be so hopeless as to see suicide as the best possible solution ought to turn to Christ who said: "These things I have spoken to you, that My joy may be in you, and that your joy may be made full." John 15:11.
I hope this helps!