Women are twice as likely as men to experience depression, a major public health problem that costs the United States $16 billion a year, officials said this week.

The American Psychological Association said patterns of thinking, physical and sexual abuse, poverty and unhappy marriages are all woven into a complex tapestry that puts women at double the risk for depression.Bonnie Strickland, an Amherst professor of psychology and past president of the APA, called depression "a major public health problem" that costs the country about $16 billion a year and leads to about 30,000 suicides a year.

"Unfortunately, it's often not recognized and untreated," Strickland said at a news conference.

The pattern of depression, she said, seems to be occurring more and more often among young adults, shifting from the middle-aged who were once the major victims. And though depression occurs at some time in the life in one out of every eight men, the disorder strikes 25 percent of all women, Strickland said.

A three-year study by a committee of experts organized by the APA found that at least 7 million American women suffer from depression and that most will go untreated, often with "tragic, unnecessary losses" such as suicide.

"Women truly are more depressed than men primarily due to their experience of being female in our contemporary culture," Ellen McGrath, chairwoman of the National Task Force on Women and Depression, said in a statement prepared for a news conference.

The study said more research is essential to determine why women are so vulnerable to the ailment, how best to treat it and how best to help women protect themselves from the dangers of profound depression.

McGrath said the task force found that women of all races, ages and income levels - in Europe, Africa and North America - are all at higher risk than men for most types of depression. And, said McGrath, the reason is not that women are more apt to admit their feelings.

"It is astonishing how often this difference is denied by assuming that women more readily report emotional distress than men," she said. "This argument says women are not really more depressed, they just say and think so."

The report by the task force said a number of social, economic, biological and emotional factors raise the risk of depression for women. Consequently, the experts said, women and their depression should be studied in a "biopsychosocial context" that recognizes the varied effects of gender differences in all these factors.

Although depression now readily yields to treatment in 80 to 90 percent of all patients, most women with the ailment go untreated, the report said.