For both topics, but especially for the format of references in the reference section, you are strongly encouraged to study the Publication Manual. Generally, there are two reasons to cite references. Some examples of these two situations follow. Some studies have shown that people are attracted to similar others. Here, the statement of fact is that people are attracted to similar others.
Schizophrenia is genetic.
Here, again, you want to make the statement of fact that schizophrenia is genetically caused. Notice two things. At most, the research suggests that your genetic makeup can enhance the likelihood that you will develop schizophrenia. Environment is also important. Here, the statement of fact refers to what people believe.