I am currently spending an exchange semester in another country.
I have moved into an apartment with several roommates due to a relatively high cost of living. I always had my 16 m² apartment for myself so I am new to living together with other people. Everything went smoothly in the first weeks. Due to my classes being always in the afternoon, I just woke up relatively late at maybe 10 AM. Now my schedule has somewhat shifted and I am more or less required to wake up at 7 AM in the morning.
Now I have noticed something that makes me very uncomfortable. A roommate also wakes up at this time and the first thing he does is to go to the bathroom and throw up. This is voluntary and occurs every morning. I do not know the reasons, I suspect psychological problems since he seems healthy in every other regard. I woke up more than once to the sound of him doing that and it is really making me uncomfortable. Others have also noticed this and we have talked about it, but the others don't really seem to care a lot.
I carefully addressed it once when I was making breakfast in the kitchen, which is right next to the bathroom, and he denied it even happened. If it was just an illness and he had it in check, he could have just said "Yeah, this is going on", which didn't happen.
I want to tell him to stop doing this, but I never had to address an issue with a roommate so far, so I have no starting point. Usually, I am quite blunt and just directly address people with issues I have, but I have experienced that in rare cases it makes the problem actually worse instead of better. This happens most often when people don't see the problem or it's a deeply personal matter. Since he denied it the first time I don't know how he would react to another direct confrontation. I am worried that he might have problems, either physically or mentally he is not dealing with, and since he is a nice guy otherwise, I don't wish him any harm.
How can I approach him to stop this, since it makes my stay, especially in the mornings substantially worse?