Maybe one way is to say, "So what do you think is causing _____(symptom/s)?"

I agree with Bud that a lot of diagnoses are made that are really symptoms associated with a host of possible causes. Often, biological reasons are overlooked as the causes of depression, anxiety and mood instability (toxins, deficiencies, poor digestion); and trauma symptoms can be mis-diagnosed as a personality disorder.

I feel fortunate to have a therapist who considers all influences. Even though she's not a physician, she encourages exploring physiological causes in addition to the ones that she can help with through therapy.

She won't give a diagnosis, even when I have asked. But, when I ask what she thinks is going on (as in, what's causing this?), it's been more productive for me.