Two out of every five veterans of military service in Vietnam have severe psychological and other problems ranging from drug abuse to nervous disorders, according to a new government-financed study.

In other areas, such as education and employment, the Vietnam veteran lags somewhat behind veterans of the same period who did not serve in Vietnam and far behind non-veterans of similar age.

These preliminary findings, disclosed last week by the Veterans Administration, were distributed yesterday by two members of Congress and Robert O. Muller, executive director of Vietnam Veterans of America.

VA administrator Max Cleland, himself a disabled Vietnam veteran, sent a copy of the findings last week to Sen. Alan Cranston (D-Calif.), Veterans Affairs Committee chairman, with a cautionary note.

Cleland warned against "drawing inferences as to conditions nationwide," but one point was clear: The early results suggest that Vietnam veterans' readjustment problems may run considerably deeper than Cleland and others in the Carter administration have acknowledged.

Cleland's letter to Cranston did not mention that the VA delayed release of the data, then freed it under the pressure of a freedom-of-information request by Muller's organization.

Among the preliminary findings:

Sixty percent of Vietnam veterans and 30 percent of veterans who were not in Vietnam said they had problems with drugs, alcohol, disease, nerves and psychological disorders upon leaving service. Forty-one percent of the Vietnam veterans said those problems persisted; the other group showed only 13 percent.

More or less equal in education before their military service, 53 percent of those veterans who returned from Vietnam did not resume their education, compared with 31 percent of those veterans who had not served in Vietnam. Military service also had "a negative impact" on later job attainment, the study added.

Meeting with reporters yesterday, Muller, Sen. H. John Heinz III (R-Pa.) and Rep. David E. Bonior (D-Mich.) -- all Vietnam-era veterans -- said the findings document the need of veterans for greater government help.

Hienz and Bonior, part of a 19-member Vietnam veterans' caucus in Congress, said they are preparing legislation aimed at dealing more directly with the problems of veterans. For months they have been in a running battle with Congress and the White House over Vietnam veterans' problems.

The findings, prepared under contract with the VA by the Center for Policy Research in New York City, deal only with veterans living in the Northeast. Other regions will be analyzed later, with a final report due next September.

Muller, Heinz and Bonior, however, predicted the center's findings elsewhere can be expected to mirror the results of lengthy interviews in Bridgeport, Conn., Brooklyn and Westchester, N.Y.