Sometimes people feel very sad, lonely, or like they don't matter to anyone else. When people feel like this for a long time, it can make them start to feel sick. They might not want to eat, sleep, or do things they used to enjoy. This can make them have a lot of health problems.
Doctors call these kinds of sicknesses "diseases of despair," because they can be caused by feeling really hopeless and sad. Diseases of despair can be really serious and affect lots of people in different ways. Some diseases of despair are depression, addiction to drugs and alcohol, and suicide.