We are humbled in the field to be organizing our diagnostic scheme by symptoms, not by clearly delineated underlying biological mechanisms. For example, what we diagnose as schizophrenia has variability in symptom presentation. Additional research is needed to help organize a diagnostic system based on underlying biology–this is the essence of the Research Domain Criteria (RDoC) effort at the National Institute of Mental Health. Until more precise science is available, psychiatric medication treatments can have partial effects for some symptoms and not address others. Every person is also different in multiple dimensions such family history, trauma history, current stressors and prior diagnoses, and medical and psychiatric medication history. So, while one medicine may work for one person with a psychiatric condition, your next patient with the same diagnosis may require a different regimen. The research on polypharmacy is also incomplete. Sharing the research uncertainty when appropriate and addressing both symptoms and side effects as well as patient experience can be good pathways forward. Clinical guidelines can be informative for how to think about adding medications and there is research to support some combination treatments. The American Psychiatric Association publishes a number of evidence-based practice guidelines.
It is important for patients and their families to understand the challenges presented in determine the best medication treatments for their specific conditions, and why changes can occur frequently at the beginning of treatment. Helping them understand that psychiatry is an art as well as a science can be helpful.