Why are mental illnesses socially stigmatized

Why are mental illnesses socially stigmatized? Mental illnesses is stigmatized because people think mental illness is a joke, they don’t actually believe in mental illness, but for some reason they believe in a mental hospital but the thought of someone having severe depression or anxiety our bipolar disorder or ADHD is a joke to them. Lot’s of people just don’t take psychology serious therefore they stigmatize every single diagnosis, because of this it actually can cause people that have these illnesses severe stress, and as we all know stress just makes illness much worse, so when you use funny names and hate these people for having a mental illness it only makes the situation worse for them. Lot’s of people don’t understand the complexity of the mind or how powerful the mind actually is, because of this they take lightly of any situation concerning mental health, mental health is incredibly important but today’s society just doesn’t understand that, it’s realistically no surprise because in the beginning of this field of psychology lot’s of people didn’t take it serious.