I Know Someone With Schizophrenia

I know a couple people with this. I am interested in the disorder and have watched some documentaries about it. Have seen a couple stories on here where people are complaining that they are unhappy all the time due to their schizophrenia. They claim they can't enjoy anything ever, and that life has no pleasure for them. I just want to ask, is this normally a symptom? Or is it something comorbid occurring with their schizophrenia? Everything I have studied about it so far has not mentioned symptoms of intense depression. So I was wondering if there are some narcissistic elements in there. When they say that people's happiness angers them, it perplexes me. I cannot imagine not being happy for other people when they are happy, even if I myself am miserable at the time. I have several mental illnesses myself.