Soviet authorities have imprisoned or restricted more than 400 dissidents in the last four years, including at least 100 forcibly confined in psychiatric hospitals, according to an Amnesty International study released yesterday.

The human rights organization said it believed scores of other dissidents have been rounded up since the study was completed last summer.

"Prisoners of Conscience in the U.S.S.R." a 200-page book, charges that the Soviet authorities use "hunger, forced labor and dangerous drugs to punish imprisoned dissenters."

The report is a followup of a similar effort in 1975, which Moscow rejected as inspired by "anti-Soviet motives." Publication comes with the approach of the summer Olympics in Moscow. Amnesty released a similar study on Argentina before the World Cup soccer tournament there in 1978.

"There are many more prisoners of conscience than those of whom we know," said the Soviet study. "The real number is veiled by official censorship, secrecy and the threat of retaliation against those who speak out against political imprisonment."

It said, "activists for greater rights for national groups have also been accused of . . . anti-Soviet intent," with those sentenced on such charges including "Lithuanians, Latvians, Estonians, Georgians, Armenians, Moldavians, Russians, Crimean Tatars and Ukrainians."

Meanwhile, Alexander Lavut, a mathematician closely linked with human rights monitoring efforts in the Soviet Union, was arrested by security police, dissident sources said. i