What document provides an insured's medical history, including diagnoses and treatments?

The attending physician's statement is the correct answer because it serves as a detailed document that provides insights into an insured individual's medical history, including past diagnoses and treatments. This statement is typically completed by the individual's physician and includes relevant information that is critical for underwriting and claims decisions.

When assessing an individual's health status, insurers often rely on the attending physician's statement to gain a comprehensive understanding of the insured's medical concerns, ongoing treatments, and any significant health conditions. This information is crucial not just for evaluating risk but also for determining coverage options.

While the other options—policy summary, health insurance application, and medical history report—are important documents in their own right, they do not provide the same depth of medical detail as the attending physician's statement. The policy summary generally outlines the terms of the insurance coverage, the health insurance application collects information about the applicant's demographics and health history but is not as detailed, and a medical history report may contain relevant facts but doesn't specifically come from the attending physician. Thus, the attending physician's statement stands out as the definitive source for an insured's medical history.