International banks cut back their overseas loans last year in a sharp break with the trend of the 1970s, two separate studies released yesterday said.

Banks across the world cut back their international lending last year, and are cutting further this year, according to a report from the International Monetary Fund, the Washington-based agency that lends money to cash-starved nations in exchange for economic policy changes in those nations.

The IMF report on world financial markets said that the lending squeeze came as a result of "heightened perceptions of risk in international lending." Net bank lending in 1982 totalled $95 billion, compared to $165 billion in 1981 and $160 billion in 1980, the study said.

The Third World debt crisis, triggered a year ago when Mexico said it could not keep up payments on its debt, has frightened many banks away from lending money to developing nations, which borrowed hugely on the world capital markets in earlier years. The IMF report pointed out that nearly half of the new bank loan commitments made in the first three months of this year were to Mexico and Brazil. These new loans were made as part of overall debt restructuring packages, where commercial banks agreed to put up money in proportion to their share of loans to each nation. This lending has been dubbed "involuntary" as banks were making the loans to ensure the safety of the money that they already had out.

Meanwhile, a separate report yesterday from the Federal Reserve Board said that the overseas assets, or loans, of foreign branches of U.S. banks dropped by 0.6 percent in 1982 to $388.5 billion, in "an abrupt change from the earlier pattern of growth in the assets of foreign branches." During the 1970s, assets at overseas branches of U.S. banks climbed at an annual rate of more than 20 percent, the Federal Reserve report said. During the 1980 and 1981 this pace slowed, but still increased about 10 percent a year.

The decline was due to three principal factors, the Federal Reserve said. One was the general cutback in world trade and finance during the recession year of 1982; another that the higher exchange rate of the dollar lowered the value of foreign currency denominated assets; and the third was the legislation permitting banks to set up new International Banking Facilities in this country for foreign assets, serving as substitutes for foreign branches.

The IMF study said that "the slowdown in bank lending was also accompanied by important shifts in the composition of borrowers." Non-oil developing countries, which had built up their overseas borrowing dramatically in recent years, took a slightly smaller share of the overall amount banks lent worldwide, it said. The share of new bank loans going to oil exporters rose, the share of industrialized nations remained steady, while there was a sharp decline for Eastern Europe.

The financial crisis in Poland scared bankers away from lending to Eastern Europe before the debt problems of the large Latin American borrowers surfaced in mid-1982.