The Athletics Integrity Unit, which prosecutes cases in track and field, said Stevens was unavailable for three doping controls in 2019 in Oregon and West Hollywood. Three whereabouts violations within one year can lead to a ban.
The third and decisive missed test came when she could not be contacted after changing her telephone number to avoid harassment by an unknown individual, the disciplinary tribunal was told.
The 25-year-old American runner's ban was backdated to start on Feb. 17, 2020. It will expire days after the scheduled closing ceremony of the postponed Tokyo Olympics in August 2021.
The ruling came while another Olympic medal prospect from the United States, men's 100-meter world champion Christian Coleman, is under an AIU investigation for missed tests. Coleman was provisionally suspended one month ago.
Stevens is a 200-meter specialist who placed seventh in the final at the 2016 Rio de Janeiro Olympics, and fifth at the 2017 world championships in London.
In the 2019 season of her missed doping controls, she did not make the U.S. team for the world championships in Doha, Qatar.
Stevens cited issues with her telephone for sample collections officials being unable to contact her for two of the missed visits, according to the published ruling from her disciplinary hearing.
On one occasion her phone ran out of battery power overnight, and another time she changed number six weeks earlier because of being harassed, the ruling stated.
“Despite our sympathy for the athlete, we have not been satisfied on a balance of probability that her behavior was not negligent,” the disciplinary panel said, noting the two previous whereabouts failures for Stevens.
“She should have been on red alert and conscious that she could not miss the next one,” the ruling said.
The tribunal did take account of “distress, fear and distraction caused by the harassment she experienced" and took six months off the potential two-year ban for a first offence.
Stevens, who was represented by one of sports' top lawyers for doping cases, Howard Jacobs, can appeal against the ban at the Court of Arbitration for Sport.
She was the 2017 national champion over 200 and a former NCAA champion in the 4x400 relay running for the University of Oregon.