An easy way to develop your thesis is to make it into a question that your essay will answer. What is the primary question or hypothesis that you are going to go about proving in your paper? For example, your thesis question might be “how does cultural acceptance change the success of treatment for mental illness?” This can then determine what your thesis is - whatever your answer to the question is, is your thesis statement.
Now that you have carefully worked through your evidence, write a conclusion that briefly summarizes your findings for the reader and provides a sense of closure. Start by briefly restating the thesis statement, then remind the reader of the points you covered over the course of the paper. Slowly zoom out of the topic as you write, ending on a broad note by emphasizing the larger implication of your findings.
If you find one really awesome book or journal that fits your topic perfectly, try looking in the works cited/bibliography/reference list at the end of it. This should contain many more books and journals that are about your topic as well.
The thesis statement is a 1-2 sentence statement at the beginning of your paper that states the main goal or argument of your paper. Although you can alter the wording of your thesis statement for the final draft later, coming up with the main goal of your essay must be done in the beginning. All of your body paragraphs and information will revolve around your thesis, so make sure that you are clear on what your thesis is.