AS A REPORTER, he had won coveted national awards for his coverage of World War II. A few years ago he retired, and at first he peacefully drove his finely tuned car, regaled his friends with old stories and enjoyed attending the races. But he began to have bouts of disorientation, and two years ago the doctor said the dread word: senile.

By last summer, when he had to go to the hospital for a brief stay, he erupted like Mount Vesuvius. Furious at his failure, he fired doctor after doctor, and cursed countless nurses. He wanted to die.

But by last week, the pervasive failure had been replaced by satisfaction for his accomplisments and confusion had yielded once again to activity -- having lunch with friends, playing gin, helping worse-off former colleagues.

A miracle cure? No. The old reporter was a victim who was lucky enough to reverse his victimization. For the "hopeless senility" the doctors had reported was in truth depression, which frequently is misdiagnosed as irreversible senility in the aged.

"It's rare for so dramatic a turn-around," said my friend Carol Hausman the other day. She correctly diagnosed and treated the reporter's depression, and in the process helped put another puncture in the too pervasive myth of senility. A psychologist, she is one of this city's few gerontologists, a growing field of specialists in the scientific study of aging.

Gerontologists like Hausman are profoundly disturbed by the tendency of too many doctors to glibly diagnose senility when the patient's difficulties are rooted in something else. And experts around the country have decalred war on this widespread form of discrimination against the aged.

Gerontologists like Hausman are profoundly disturbed by the tendency of too many doctors to glibly diagnose senility when the patient's difficulties are rooted in something else. And experts around the country have declared war on this widespread form of discrimination against the aged.

It is an irrational practice, for we are rapidly becoming a country of the aged, and the over-75 age group is the fastest-growing in the nation. By the year 2000, elderly Americans will constitute 15 percent of the population if current trends continue. In Washington, the number of persons over 65 was 67,000 in 1976 and 73,000 in 1978.

Hausman helped the former reporter basically by just becoming his chronicler, encouraging him to review his personal history in minute detail with a view toward self-enhancement.

The professionals say that old people who live with their families and have people to talk to fare better and have a vitality that is missing from the solitary aged and those who live in institutions. I know this is true for I have watched my 85-year-old mother-in-law, who has the responsibility of caring for her great-great-grandchild in her home, also go to work as a foster grandmother each day from 9 a.m. until 2 p.m.

The reporter didn't want to be identified by his real name in this column. That's a telling indicator of how old people still shy away from acknowledging they have had professional help lest they be written off as crazy. For they are as scared of losing their minds as they are of becoming senile.

"I believe more people fear senility, fear growing old and losing their minds and being put away, than fear cancer," says Dr. Robert N. Butler, director of the National Institute on Aging in Bethesda, who developed the life review concept Hausman used.

It was the reporter's somewhat younger wife who summoned Hausman to the hospital where her husband was behaving so wildly. Visiting 10 minutes each day, Hausman avoided identifying herself as a psychologist.

"Why do you want to bother with a useless old man like me?" he's ask querulously.

But gradually he began talking, giving his oral history. He spoke of starting in the newspaper business as a lad of 12 by working as a go-fer for an older man; of reporting on President Harding in the 1920s, and on Eleanor Roosevelt in the 1930s.

"Do you think I'm senile?" he'd worked up the courage to ask by the third month. Hausman's negative answer helped further boost his now-lifting spirits.

By the therapy's end, the reporter realized how valuable his life had been, and how proud he was of helping young reporters. "If you don't have enough guts to talk back to the boss, you don't have guts enough to be a reporter," he recalled having counseled them.

"I'd like to walk into a restaurant with him and see the doctor's face who told him he was senile," Hausman said with delicious malevolence.

Not every life-eroding depression can be lifted so dramatically. For if depression is a major problem in the overall population, it is an epidemic for the aged. And for good reason: It's a time of incredible losses -- friends and spouses, income, health, job, housing, power.

When he was "cured," the reporter's parting shot gave pleasure to Hausman.

"But Doc," he said, with a hangdog expression, "I'm so sick." She was pleased that finally he could accept his chronicler as his psychologist.