Use reference books to get an overview of topics available to you, and to help you select something to research. These are to be consulted for INFO only, they should never be cited as a resource in your paper.
Reference books (encyclopedias, dictionaries, handbooks, manuals) can be very useful when seeking basic, factual information about a disease, condition, affliction, or treatment of those.
Always ask a Reference Librarian if you need help!
Diagnostic and Statistical Manual of Mental Disorders (DSM-IV-TR)
Mental Health Disorders Sourcebook
Encyclopedia of Applied Psychology
Popular Psychology: An Encyclopedia