Gryffindor: at first they'll be angry. They'll question the things that are happening in their life. Why them? Why did this happen? Then it will turn self-destructive. They'll binge, they'll lock themselves away. They pull back from their activities and their immune system plummets for some reason. They have much more mood swings, like a time bomb with no clock for detonation

Ravenclaw: the recluse type of sadness. They won't speak as much or show interest in their favorite things. Ravenclaws will sleep even more than normal and always use the tired excuse but the light in their eyes aren't shining anymore. They need to be shaken awake as if it were a bad dream. If you can set them on the right course they'll realize what's wrong as well

Hufflepuff: the type that you feel constantly. Soft people aren't weak. They're strong enough to let their emotions show, remember that. Their sadness will show on their face, in their decisions. Hufflepuffs need someone to save them from themselves when they slip into sadness, luckily most have found loyal friends who will stick next to them through thick and thin

Slytherin: they turn numb. The hardest to pick out exactly what's wrong with them. They hide their pain really well because in their mind pain is a weakness and they would rather die than show their weakness. Become distrustful of everything they once thought was stable. Need someone to help them but not large enough for the Slytherin to notice or they'll refuse the help