The Diagnostic and Statistical Manual of Mental Disorders (DSM) is the handbook used by health care professionals in the United States and much of the world as the authoritative guide to the diagnosis of mental disorders. The last edition (5th, DSM-5) was published in 2013.
The DSM provides a common language to establish consistent communication and reliable diagnoses among clinicians and for researchers to study the improvement of medications and other interventions.
See Section 10.2.32 of the APA Manual and the APA Style Diagnostic Manual References
When referring to the whole book:
American Psychiatric Association. (2013). Diagnostic and statistical manual of mental disorders (5th ed.).
**Because the author and the publisher are the same, “American Psychiatric Association” is written only in the author element.
When referring to specific sections of the DSM-5:
American Psychiatric Association. (2013). Anxiety disorders. In Diagnostic and statistical manual of mental disorders (5th ed.).