How could a case study be used to learn more about mental illnesses?
A case study is an extensive observation of a subject/s, Observation is the a scientific methods, which usually includes multiple testing, interviews, data analysis and many more.
In learning more about mental illnesses, A case study is necessary to determine, the possible causes, symptoms and treatment of mental illnesses. A case study is also used to compare and differentiate, a mental illness from another illness, to avoid possible complications from incorrect treatment or medication.
Something as basic as a medical diagnosis, can be considered as a case study. The greatest product of multiple case studies, is the Encyclopedia of Psychology and Mental illnesses. The mighty "Diagnostic and Statistical Manual of Mental Disorders" with is recent version (DSM-5).