As a psychotherapist, I never put anything in the chart that would cause my patient pain if known by another, e.g., Mrs. X tells me she is having an affair with Pastor Y or her neighbor, Mr. M was not put in the chart. The court could subpoena my chart, but not what was in my head or heart. By law, I was required, and did, document and report information concerning child abuse and other felony crimes, but that happened very rarely during my years of practice.
All the insurance companies required of me was to document sufficient symptoms to validate the diagnosis, make a note each session to confirm I saw the patient on that date, and was property treating said diagnosis. I could touch the required diagnositic bases of depression, for example, by saying Mrs. X was anhedonic, sleeping poorly, had poor appetite, felt worthless, etc., giving details of the symptoms without having to metion her affair. (To an insurance company Mrs. X was merely a diagnosis to be treated, not a person.)
I well knew that any time I submitted records to an insurance company or to another clinic the record then could easily become public information.