Studying schizophrenia (SZ) right now at A2 level, an idea is:
-Psychological and biological explanations of SZ (evaluate and compare, including pros/cons for both)
-Psychological and biological treatments of SZ (evaluate and compare, including pros/cons for both)
-Diagnosis and issues with the diagnosis of such condition (DCM-IV and ICD-10)
All come up on my a-level exam board at A2 level, and the diagnosis, explanations and treatments are the 3 main areas you will study. (worth checking exam board you will be studying though!)