October 8, 1985

THE anguish that leads to suicide seems to follow no set path. But researchers believe they are making important progress toward understanding that painful process. They have identified a deficiency of a specific chemical - serotonin - in the brains of some people who are prone to take their own lives in the face of life's difficulties. Some researchers believe as a result that biological factors may play a far greater role in the events that end in suicide than has been realized. And the hope now is that a drug could eventually be developed to correct the chemical deficiency and prevent at least some future suicides.

Columbia University's board of trustees voted yesterday to sell, ''in an orderly way'' over the next two years, virtually all of the university's $39 million in stock in American companies doing business in South Africa. Columbia thus became the first Ivy League school to join the growing roll of colleges, state and local governments and other institutional investors that have chosen divestment to protest South Africa's racial policies, known collectively as apartheid. The divestment, to be completed by October 1987, will involve the sale of about 4 percent of Columbia's $900 million portfolio, and will include stock in such companies as American Express, Burroughs, Chevron, Coca-Cola, E.I. du Pont de Nemours, Ford Motor, General Motors, International Business Machines, Mobil Oil, Phillips Petroleum and Sperry. Vote at Closed Session Consideration will be given to ''appropriate exceptions,'' such as stock in news-media companies with bureaus in South Africa, the board said. The vote was taken at a closed session of the 24-member board and the tally was not announced, as is customary.

Heavily armed men hijacked an Italian cruise ship with more than 400 people aboard in the Mediterranean on Monday and demanded the release of 50 Palestinians from Israeli prisons. The leader of the hijackers, reportedly members of a militant Palestinian faction, was said to have warned that the first hostages to be killed would be Americans. It was unclear how many Americans were still on the ship. A spokesman for the cruise line said from California on Monday night that 62 Americans had been registered for the cruise. An Italian Foreign Ministry report said 72 Americans were listed as passengers.

International Commandos hijacked a cruise ship with more than 400 people aboard in the Mediterranean. The heavily armed hijackers, identified as Palestinians, demanded the release of 50 Palestinian prisoners being held in Israel. The leader of the commandos was quoted as saying that the first hostages to be killed would be Americans. Unconfirmed reports on the state-run Italian television said that 28 Americans were on board the Italian cruise ship. The hijackers were quoted as saying they would blow up the vessel if a rescue mission was undertaken. [Page A1, Columns 4-6.] Major aid for drought-stricken nations of sub-Saharan Africa is set. Financial leaders from around the world agreed to set aside $2.7 billion from the International Monetary Fund for a special lending pool to help the poorest countries promote economic growth. Countries eligible for the loans are those whose average per capita income is below $410 and that have problems paying off bank loans and generating enough foreign currency to pay for key imports. [A1:1.]

In the aftermath of rioting in the north London district of Tottenham in which a constable was killed, the police warned today that they would be prepared to use plastic bullets and tear gas in future confrontations with rioters. The Home Secretary, Douglas Hurd, said the police would have the Government's ''full support'' if they found it necessary to resort to new methods of control. ''It is absolutely vital that the police have the equipment they need,'' he declared. In fact, riot policemen were reported to have been armed early today with both plastic bullets and gas canisters - which have yet to be used in a civil disturbance in Britain - when they swept through the Broadwater Farm housing project just before dawn. They met no resistance, however, from the racially mixed crowd of youths that had been driven back during the night onto the grounds of the project and contained there.