Teens often are better at adjusting to life than their parents believe, says a doctor who led a study of 6,000 middle-class high school students in the United States and nine other countries.

Dr. Daniel Offer, director of the Center for the Study of Adolescents at Chicago's Michael Reese Hospital, said in an interview that he's optimistic about "who will inherit the Earth.""I don't think we're leaving the world in the hands of groups that are going to go off the deep end . . . and they might even do a better job of it," Offer said Sunday.

The results of his research, conducted mostly in 1984 and 1985, are the subject of a new book, "The Teenage World," published by Plenum Medical Books of New York.

The teens surveyed were from Australia, Bangladesh, Hungary, Israel, Italy, Japan, Taiwan, Turkey, West Germany and the United States.

Offer concede the results might be skewed because they covered only middle-class teenagers. And one psychiatrist cautioned that psychological profiles based on the survey may be superficial.

For the study, between 500 and 1,000 teenagers in each country completed a psychological "self-image" questionnaire of 130 items translated into their own languages.

At least 100 boys and 100 girls in the 13-15 and 16-19 age groups were surveyed by local researchers in each country, Offer said.

The survey found that at least 73 percent of the youths in the 10 countries have a healthy image of themselves. It found them to be generally self-confident, optimistic about their career goals, with realistic social concerns.

And more than 90 percent of the teenagers in each country said they felt good about their parents and their values.

Only 12 percent felt they would not be able to take care of themselves in the future. Offer said that contrasts with the image of teenagers "as foundering, impulse-ridden and oriented only to immediate gratification."

"What impressed us is that the majority of teenagers are optimistic about their future and their main concern is economic, getting a job that pays a good living," Offer said.

"There are differences, but there is the concept of a global village and kids are becoming more alike."

He said the survey found similar differences between the sexes in each country - for example, he said, girls had a higher degree of social awareness and a commitment to others while boys coped better with solving problems and showed more control of their emotions.

The survey also turned up some distinct national characteristics. Israel and American teens, for example, were the most confident, while Taiwanese were most likely to be confused.

American teens tended to have more difficulties with relationships among families and friends than teens in other countries, Offer siad.

Dr. Richard C. Marohn, professor of clinical psychiatry at Northwestern University, said Offer's research is important, but added, "it doesn't answer all the questions we have about teenagers."