Junior Seau Completely Sober When He Died

TMZ obtained the autopsy report, filed by Deputy Medical Examiner Craig Nelson ... which shows Seau died of a self-inflicted gunshot wound to the chest on May 2, 2012.

The report also shows "No alcohol, common drugs of abuse, or other medications were detected."

However, a small amount of Zolpidem (aka ambien) and Naproxen (an anti-inflammatory) were detected ... but the M.E. says test results were "consistent with therapeutic use."