Zaghari-Ratcliffe, a project manager with the Thomson Reuters Foundation, was moved to the psychiatric ward of Imam Khomeini hospital in the capital on July 15, the "Free Nazanin" campaign group run by her husband said last week.
"Nazanin has been returned from psychiatric hospital, and is now back in Evin prison," her husband, Richard, said in a statement. She was discharged at her request and the request of the hospital doctor, the campaign group said.
Zaghari-Ratcliffe was told she had been admitted to hospital for a 10-day period of assessment. She received psychotherapy sessions, had physical checks and was prescribed some medicines, the campaign group seeking her release said.
In its release, the group quoted Zaghari-Ratcliffe saying that she was kept in a private room measuring 2 meters by 3 meters (6.5 feet by 9.8 feet) and was handcuffed and chained to the bed day and night.
The Iranian embassy in London declined immediate comment on the case.
"They did all they could to me – handcuffs, ankle cuffs, in a private room 2x3m, with thick curtains, and the door closed all the time," she was quoted as saying. "I wasn’t allowed to leave the room, as I was chained to the bed."
British Foreign Secretary Jeremy Hunt told parliament the fact she had been moved back to prison was "a positive sign."
"The way that she was detained for a week without being able to have any access to her family was totally unacceptable and I am afraid all too predictable from the Iranian regime," he said.
Zaghari-Ratcliffe was arrested in April 2016 at a Tehran airport as she headed back to Britain with her daughter after a family visit, and was sentenced to five years in jail after being convicted of plotting to overthrow Iran's clerical establishment.Her family and the Foundation, a charity organization that operates independently of Thomson Reuters and Reuters News, deny the charge.