Drug abuse and trafficking lessened in some developed countries last year but grew in parts of the Third World, a U.N. survey reported this week.

Compiled by the International Narcotics Control Board, the study noted trends suggesting a drop in overall drug abuse in Western Europe and of crack cocaine in North America.However, criminals in Africa used new intercontinental air links to increase the domestic drug trade, while domestic consumption of cocaine grew in South and Central America, according to the survey.

In the Andean countries, the report said, cocaine production increased last year despite attempts at eradication.

The number of Soviet drug abusers, mostly of marijuana, almost doubled over the past five years to reach an estimated 140,000, said the study by the Vienna-based board, which works with the World Health Organization and other U.N. agencies.

A summary by region:

- Europe: Crack use remained negligible, but cocaine smuggling into Europe, mostly from Colombia, increased.

In Western Europe, "the average age of abusers has risen, suggesting a decline in the number of new abusers," the report said.

- North America: The social and economic cost of drug abuse in the United States was estimated last year at $60 billion. On a positive note, the report noted an apparent lessening in crack cocaine use, with a drop in attributable deaths and hospital admissions.

In Canada, marijuana and cocaine remained the drugs of choice.

- Africa: Drug abuse spread to the entire continent over the past few years. Much of it was heroin, originating mainly in Southwest Asia and destined for Europe or North America.

Cocaine trafficking increased, due partially to the new regional air links and increased use of heroin routes for cocaine.

- South America: Increased violence was seen in Colombia and Peru as the war on producers and traffickers escalated.

- East and Southeast Asia: Illicit opium production in Southeast Asia doubled in 1988-1989 from the previous year to about 2,000 tons and remained at the same high level last year.

Cocaine seizures in Japan increased fivefold.

- Oceania: The report estimated 90,000 to 130,000 heroin addicts in Australia.

- South Asia: Drug abuse rose in Bangladesh, with an estimated 50,000 users alone in Dhaka, the capital. Drug abuse also rose in India's major cities.

- Near and Middle East: Afghanistan reported that 580 tons of opium were produced and 3,480 acres cultivated with marijuana in 1989, compared with 120 tons and 1,235 acres in 1976.