Well, I think they are working on the sophistication of these types of tests. My son had them done with regards to medication. People pay big money for this testing and it was part of our inpatient psychiatric hospital stay for my husband. When I got the report, I was like . . . ya. For us, it revealed nothing. They tell if meds are metabolized. My son metabolizes everything. Does NOT mean that he tolerates the medication as he tried one on the list and it was a huge NO go with massive activation, insomnia for 48 straight hours. The report said he'd do as well on it as any other med. In terms of diagnosing, it seems the answer to if genetic testing can determine your diagnosis? Currently, the answer is no. Here's a good article about that. https://www.nimh.nih.gov/health/publications/looking-at-my-genes I do think an MRI can show your brain and abnormalities and those with mental health issues can have a different looking MRI. But interpreting diagnosis from it is not really done. Usually, symptoms are taken, questionnaires, observation. My son as been through a lot of assessments. Do I feel his diagnosis is accurate, yes.
I think you believe there are professionals on this website, and that's not true, we are all just folks with either an interest or experience with specific problems. Many years ago there were medical professionals also on here but no longer. I will say, though, that if you are talking about mental illness, I don't think you're going to get an answer to your question. Over the many years I have fighting with mental illness there have been a great many claims that diagnostic testing can determine what medication would be best for a particular person or what neurotransmitter receptors are misbehaving, but none of them has proven to be more than a way of making money for a small number of clinicians. In the end, when it comes to actual treatment, it's still all trial and error. Diagnosis is still done based on the patient reporting symptoms, which demands the practitioner believe the person is actually reporting what's happening without doing any independent investigation, such as going to the person's home and interviewing friends and family to see if the patient is actually manifesting what he says he is. That would be much more objective, but it isn't done by anyone. Nobody knows if mental illness is genetic or not, as no family has everyone in it having the same mental disorder. So why one person and not his siblings? Nobody knows. Again, all trial and error. Peace.