VA Medicinal Cannabis Research Act of 2021 This bill requires the Department of Veterans Affairs (VA) to conduct clinical trials of the effects of medical-grade cannabis on the health outcomes of covered veterans diagnosed with chronic pain and those diagnosed with post-traumatic stress disorder. Covered veterans are those who are enrolled in the VA health care system. The trials must include a control group and an experimental group that are of similar sizes and structures and represent the demographics of the veteran population. Data collected in the trials must be preserved to facilitate further research. Under the bill, participation in the clinical trials does not affect a covered veteran's eligibility or entitlement to other VA benefits.