What this study is saying is that when we compare people with schizophrenia who are admitted to the ICU with other people admitted to the ICU , the people with schizophrenia are more likely to be in the ICU due to sepsis (an infection throughout the body) and less likely to be there due to surgery or a heart problem when compared to people of the same age/race/sex who are admitted to the ICU. The people with schizophrenia are more likely than the age/race/sex matched comparison group of other people in the ICU to have respiratory, renal and neurological problems (all are associated with sepsis) and they are more likely to die.
We cannot tell from this study if people with schizophrenia are more or less likely to get sepsis than the general public (we don't have the denominator of all people with schizophrenia) or if they are actually less likely to get surgery or heart disease compared with the general population.
There may be some reasons why people with schizophrenia are more likely to develop sepsis including a greater likelihood that they ignore signals from their bodies that they have an infection until it has spread and become very serious. They may also have poorer access to care so that they do not come to medical attention for an infection until it has progressed to sepsis.
I can not think of a relationship that would lead us to suspect that the family members of people with sepsis would be at high risk for mental illness.
