One of the main obstacles that surround the study of psychological disorders is the taboo that surrounds them in most cultures. A taboo is an implicit agreement in society to avoid discussing a topic because it is considered repugnant or inappropriate. Mental disorders are often treated that way, which means that patients will often not seek medical help or when they do, are stigmatized for doing so.
Other possible obstacles could be ethical reasons, lack of funding or lack of incentives for psychologists.