There's a reason why these tests aren't standard practice. Despite all the talk about mental illnesses being caused by "chemical imbalances", there's very very little evidence to support it. What's more, we don't really know how any neurochemicals really work in the brain, what their function is, or what the ideal range of values truly truly are. At least, there is no scientific consensus to any of these issues.
In other words, these tests don't have much practical value in medicine. They don't reliably predict symptoms of any mental health issue or indicate which treatments will be most beneficial. At least not yet.
In other words, these tests don't have much practical value in medicine. They don't reliably predict symptoms of any mental health issue or indicate which treatments will be most beneficial. At least not yet.