Hard agree. Especially since modern farming methods create food with much less nutritional value than it used to have. But nobody gets rich off of magnesium supplements, so we don't check magnesium levels for anxiety (for example).

If you have a health problem, make sure to try to have a problem that has a lucrative treatment.

Definitely, even without screening, the first step should be a prescription for basic OTC nutrients for which people are often deficient and that are associated with depression, zinc, vitamin D etc...

Similarly, most of the time people leave the doctor with a prescription for paracetamol and an advice to monitor the symptoms and come back a short while after if the symptoms don't improve.

It's simply a low cost and efficient first step of the diagnostic.