how long must you keep clinical study records
For example, psychologists, MFTs and SWs in CA should keep adult records for at least 7 years. (More info at California Law for Records Retention). Check with your licensing board, state law, institution's guidelines, or your state professional association regarding the length of time that you must keep records.
OSHA rules require that medical records must be retained for the duration of employment plus 30 years. (CMA On-Call document 1160, page 2). In general, you know your patients. The safest way to proceed is to maintain the charts of patients with complicated medical histories indefinitely.