Mr Wang is one of more than 3,000 political dissidents, trade unionists and members of the Falun Gong sect whom the campaign group Human Rights Watch (HRW) believes have been locked up in the hospitals - run by police - since the early 1980s. The word ankang means "peace and health".
Despite Chinese government claims that Mr Wang was paranoid and delusional, Dutch psychiatrists released a report showing that the 56-year-old dissident was mentally sound. "There was no reason Mr Wang had to be locked up in a special forensic psychiatric hospital or to be admitted to any psychiatric facility," the Global Initiative on Psychiatry and HRW said.
Declared criminally insane after he staged a one-man demonstration in Tiananmen Square in 1992, Mr Wang was held on a ward for violent criminals and forced to watch fellow inmates having electric shock treatment. He saw two deaths, one from a heart attack during treatment and one during force-feeding. He himself was forced to take anti-psychotic drugs.
In January this year, five months after he was released, partly as a result of German government pressure, he was examined in Germany by a team of Dutch doctors.
"It clearly proves that there were no psychiatric grounds for my 13 years in the Beijing ankang," Mr Wang said from Frankfurt, where he now lives with his wife and daughter. "I've been waiting for this for so long. It's justice at last - a great success."
Mr Wang was involved in the Beijing protests in 1989 that led to the Tiananmen Square massacre and was jailed after he tried to unfurl a protest banner on the third anniversary. Diagnosed as "suffering from paranoia", the Chinese government insists he is still mentally ill and needs "strict guardianship".
The Dutch medical report brings a spotlight to bear on Beijing's human rights policies ahead of President Hu Jintao's visit to Washington next month. China freed a New York Times researcher yesterday and several other prominent dissidents in a move that human rights groups say is an effort to smooth a path for the visit.
China unexpectedly dropped charges of revealing state secrets against the reporter Zhao Yan. His lawyer expected him to be released within days, although it remained unclear whether Mr Zhao would be sent abroad afterwards. He was detained after a story before the National People's Congress last year detailing a row between the former leader Jiang Zemin and his successor, Mr Hu.
Security officials accused Mr Zhao, already well-known as a campaigning journalist before he started working for The New York Times in 2004, of leaking details of the rivalry, and he faced 10 years in jail.
Also this week, a Tibetan Buddhist nun, Phuntsog Nyidron, who served 15 years in prison on political charges, was allowed to leave China. She has flown to the United States.
President Hu's trip is vital to foster growing trade links and smooth relations which have been strained over what Washington says is China's refusal to allow its currency to float more freely.Reuse content