The condemnation this week of protester Mikhail Kosenko to forced psychiatric treatment has sparked debate that Russia is returning to the Soviet practice of punitive psychiatry to silence its critics.

Kosenko, who had been taking medication for several years for a mild form of schizophrenia, was given a new, more serious diagnosis during his 16-month arrest, and declared dangerous and in need of indefinite isolation from society in a report cited by prosecution.

Russian veteran rights campaigner Lyudmila Alexeyeva called Tuesday's verdict against 38-year old Kosenko "a return to Soviet psychiatric persecution of dissidents" and said she will complain to the World Psychiatric Association.

Amnesty International also condemned the verdict as "abhorrent use of punitive psychiatry to silence dissent" and a breach of trial procedure.

Kosenko, who was convicted of assaulting a police officer at an anti-Vladimir Putin protest on May 6, 2012, was declared insane and dangerous due to his "paranoid schizophrenia" by Russia's Serbsky Institute in July 2012.

The same institute was behind a wave of diagnoses used to lock-up Soviet dissidents in the Soviet era, with the practice becoming especially widespread between mid-1960s and the breakup of the Soviet Union.

"The psychiatrists of the Serbsky Institute... are as unprincipled as in the Soviet times, and are also carrying out political orders, which is even more dangerous," wrote Natalia Gorbanevskaya, who herself was committed into asylum for over two years after protesting the Soviet invasion of Czechoslovakia in 1968.

'Worse than prison'

Kosenko's conviction was the third handed down against protestors who took part in the protest on Bolotnaya Square in central Moscow on the eve of Putin's inauguration for a third term.

Over a dozen more accused are still awaiting their verdicts, in a trial denounced by activists as a throwback to Soviet repression.

Kosenko had been diagnosed with light mental illness since 2001 after suffering a concussion in an army hazing incident. He had not been committed full-time into an institution before his verdict, however.

The term 'sluggish schizophrenia' used to describe Kosenko's mental state is not an internationally classified diagnosis. It was first coined by Soviet psychiatrist Andrei Snezhnevsky and was used against dissidents with "reform delusions".

Snezhnevsky, who also served as the director of the Serbsky Psychiatric institute in the Stalin era, personally confirmed diagnoses for several dissidents, and even Nobel laureate poet Joseph Brodsky who later recounted torture-like treatments like sulphur shots and said that such punishment was worse than prison.

Russian punk rock singer Yegor Letov, who was sent to a psychiatric clinic for five months in 1985 wrote after that he was given antipsychotic drugs in doses so high that he temporarily lost his vision.

The extensive report by European Parliament this year concluded that Russia's opaque system of psychiatric care barely reformed since the Soviet time and officials in recent years "feel they have the liberty to revert to using psychiatry as a tool of frightening their opponents".

"If the person is outspoken, it's easier to explain his non-agreement with authorities on psychiatric illness," said lawyer Irina Khrunova who had several recent clients condemned to forced treatment, including a blogger in the Altai region who criticised a local governor.

"In the Bolotnaya trial they want to show that only marginals and psychos protest," she said.

The head of Russia's independent psychiatric association Yury Savenko, who dismissed the Serbsky Institute's report on Kosenko as unprofessional, said the number of politically motivated diagnoses has been growing during Putin's rule, though the trend has not yet approached the massive scale of the Soviet years.

"It's the triumph of Soviet style," he told AFP. "It's a reprisal and a signal to society, they are shaking a finger and saying, this is what will happen if you don't stop protesting."