Almost everybody fits into one of three basic personality groups, almost from the moment of birth, some authorities believe.

"Alphas" are the slow, solid type. "Betas" are spontaneous, active, outgoing.

"Gammas" are moody, irritable, often demanding, often brilliant, yet often mixed-up and confused.

And gammas suffer far more early death and disease, including cancer, heart disease and emotional troubles, than other personality types, a Johns Hopkins research team has reported.

The finding, the researchers say, represents the first time anyone has linked premature death and disease to inborn temperament, the distinctive personality traits that are often seen even in newborn babies.

The finding was also a surprise to the Johns Hopkins scientists, Drs. Barbara Betz and Caroline Thomas.

In a unique project, Thomas has been following the health of Hopkins medical graduates since 1948. She is currently keeping track of 1,337 graduates of classes from 1948 to 1964.

A few years ago, Betz, a psychiatrist, reexamined the psychological records and up-to-date histories of the first 45 students - 43 men and two women - in the class of '48. They are now for the most part practicing doctors in their late 50s.

Betz classified eight as alphas. In more detail, this means people who are in more or less degree: cautious, equable or steady, well-oriented. They are people who take in the whole situation then work away at a part at a time, who take in new things gradually but adjust, and who ask little and depend on themselves.

She classed 15 as betas: generally rapid, bright and clever, blithe, light-hearted, relating to the present rather than worrying about the future, adapting well, not demanding but articulate in voicing what they do ask.

She classed 22 as the more complicated gammas: irregular and uneven, often brilliant, yet either overcautious or undercautious, overdemanding, moody, often mixed and confused before adjusting to new situations. They are persons who "take in too much or too little" and "well in focus or far out of focus."

Among these up-and-down gammas, 17, or 77 percent, had suffered various disasters or disorders: suicides, mental illnesses or lesser emotional disturbances, cancers, high blood pressure, heart attacks.

Among the slow but solid alphas, only 25 percent had such incidents and among the blithe, quick betas, only 26 percent.

Eager to check these striking results, Thomas extracted the records of 127 male graduates from the classes of 1949 through 1964.

Their records showed 64 were healthy, 63 had developed some problem. Thomas then asked Betz to classify the 127 by personality, without telling Betz which were healthy and which weren't.

Of Betz's newly designated gammas, it turned out, 61.7 percent still fell into the group with the most serious disorders, compared with 46 percent of the alphas and 33 percent of the betas.

In short, wrote the doctors in the current Johns Hopkins Medical Journal, more studies are needed to establish the facts, but there may be an inborn "thread of vulnerability" - or invulnerability - running through all our lives.

What can a gamma - or someone who thinks he or she is a gamma - do about it?

First, Thomas said yesterday, don't worry too much: "Gammas aren't all that different. They don't have a 50-50 chance of a premature disorder. They have maybe a 5 or 10 percent chance. Whatever they are, most people live a full length of life."

Second, she said, inborn temperament is at most only one determinant of disease. Other may include smoking, alcoholism, obesity, exposure to stress and other elements of life style that are usually subject to some control.

Betz, now a Kaiser health plan doctor in Los Angeles although still connected with Johns Hopkins, said: "The most sensible thing you can do is understand yourself, and try to find people who will let you be yourself."

Society - and parents, she said - need "to begin to think about a person's individuality, and assist that person according to his own innate temperament instead of trying to mold him."