It is impossible to commit suicide by holding your breath.

It is impossible to commit suicide by holding your breath.

Eventually you have a reflex or a deep exhalation to get stagnant gasses out of your lungs such as carbon monoxide and nitrogen. Even if you can force yourself to overcome this reflex you would eventually pass out from lack of oxygen to your brain. After passing out, your mouth would open and your lungs would involuntarily begin to function again.