Is it true that stress can cause biliary problems, gallbladder polyps and gallstones?

Yes, stress can also cause gallstones (common in women because of the more sensitive nervous system), as it can close the Vater's papillae leading from the gallbladder to the duodenum, preventing the sphincter of Oddi from opening, so that bile can condense in the gallbladder, causing stone formation.
As a consequence, the duct between the liver and the gallbladder may also become stiff/thickened.
You can try opening the Oddi sphincter with an occasional No-Spa 80 mg antispasmodic tablet. Stonewort (capsules or tea) has also been effective in dissolving calcareous stones in many people. If you also have digestive problems, taking GALLMET capsules is recommended.
We recommend drinking 2-3 litres of non-carbonated water a day!
The relationship between stress and bile function and digestion