I can attest that with my own experience. I had got sick with a waterborne parasite when I was a teenager. My shitty docter refused to sample my stool and insisted I take anti anxiety and antidepressants. I refused and I'm nearly certain he was paid to push those medications as I had no mental symptoms, my problems were all related to eating, digestion, and defecation.

After 6 months without treatment I had finally got tested and prescribed some strong antibiotics. This was years ago and my gut still is not the same, I had to modify my diet and rebuild what i could digest over the course of 2 years.