Schizophrenia is more common than many realize. Over 23 million people in the world have it. There are around 12 million males in the world who have been diagnosed with Schizophrenia and around 9 million females. That is a lot! But, compared to other mental disorders, it is certainly not the most common. Depression is far more common and other mental illnesses like Schizophrenia.
If someone is diagnosed with Schizophrenia and gets right on medications and has an ongoing form of therapy, you might not even realize they have it. That is one reason that it is more common than you might think. And, since many people are just not looking to diagnose others, that is another reason. The fact of the matter is it is not considered actually common but neither is it uncommon.