Vietnam veterans who saw heavy combat have had lower earnings, higher divorce rates and less "general happiness" than those who served in less stressful circumstances, according to a study released yesterday.

Described as one of the largest studies to date on Vietnam veterans, it found that those with the most intense combat experience appear to average between $3,000 and $4,000 less in annual income than other veterans of the era.

"These men appear to be literally paying a financial cost, as well as emotional . . . for their combat experience," the authors wrote, citing a "clear and consistent adverse social effect of exposure to traumatic combat situations" among the veterans studied.

Nearly 7,000 Vietnam-era veterans selected at random from the membership of the American Legion were surveyed for the study, sponsored by the Legion in concert with Jeanne M. Stellman, an associate professor at the Columbia University School of Public Health, and her husband, Steven D. Stellman, assistant vice president for epidemiology of the American Cancer Society.

Because most veterans in the study were white and all had joined the Legion, Jeanne Stellman said, "We consider these findings a 'tip of the iceberg' or 'best case' result . . . . In fact, we are aware that some Vietnam veterans have disassociated from society and moved into the wilderness."

Two to 3 percent of those sampled were black, Stellman said. About 12.5 percent of the U.S. forces in Vietnam were black.

Mike Leaveck, spokesman for the Vietnam Veterans of America, said the study probably paints a rosier picture than is the case because it limited itself to a group that is "less alienated, experiencing less problems, and more resocialized into the American fabric" than many veterans who did not join the American Legion.

The Legion study's findings are in line with earlier, smaller studies. In addition, a Washington Post-ABC News poll completed in March showed similar discrepancies between veterans of light combat and heavy combat. It also showed that most Vietnam veterans have successfully reentered the mainstream of American life.

The Legion study found the negative effects were most severe among veterans born from 1944 through 1949, the age group serving at the time of heaviest fighting by U.S. forces in Vietnam.

Among those born in 1944-45, for example, the mean income level was $21,199 a year for those who served in Southeast Asia but did not see combat, and $21,149 among those who served outside Southeast Asia. But among those who saw the highest level of combat, the mean income was $18,039.

In general, heavy-combat veterans earned less than other veterans in the same age group.

Among other conclusions:

*Close to 1 in 5 of the heavy-combat veterans reported having been divorced, compared with about 1 in 10 of the light-combat veterans.

*The attitudes of the group as a whole are very negative toward the Veterans Administration, but were less negative among those with VA contact.