More than 16 million U.S. adults experience an episode of major depression each year, and it is one of the country's costliest public health conditions. The annual cost of depression-related medical care and lost productivity is estimated at $210 billion.

The researchers found that out of a total of more than 240,000 patients who received a new diagnosis of depression in a primary care setting, 35.7 percent initiated antidepressant medication or psychotherapy within 90 days of their diagnosis. Among those with more severe depression, about half started treatment.

In addition, the researchers discovered stark differences between racial and ethnic groups and age groups. The odds of Asians, non-Hispanic blacks, and Hispanics starting treatment were at least 30 percent lower than non-Hispanic whites. The study also found that patients who were 60 years or older at the time of diagnosis were half as likely to begin treatment as patients under the age of 44.

"There was some older, more limited evidence that many people who are diagnosed with depression do not begin treatment, for reasons ranging from stigma to challenges accessing behavioral health services," said Beth Waitzfelder, PhD, lead author and investigator with the Kaiser Permanente Center for Health Research in Honolulu. She added that additional evidence has shown that some patient populations are particularly vulnerable to being untreated.

“我们的研究,远远大于以前的圣udies, provides important new evidence about the current scope of the problem among leading health care systems across the country that are striving to improve depression care in primary care settings," said Waitzfelder. "Screening for depression in primary care is a positive step toward improving detection, treatment and outcome for depression, but disparities persist. We need a better understanding of the patient and other factors that influence treatment initiation."

Using electronic health records, insurance claims and demographic data, the researchers studied patients who received a new diagnosis of depression in primary care settings in five large health care systems between 2010 and 2013. These organizations, including Kaiser Permanente and HealthPartners -- are all members of the Mental Health Research Network, a consortium of 13 health care systems that, together, provide care for more than 12 million people.

For patients who did initiate treatment, more than 80 percent started antidepressant medication rather than psychotherapy. The researchers found that older patients were less likely to choose psychotherapy, with 25 percent of patients age 18-29 starting counseling, compared to 7 percent of patients age 75 and older. All racial and ethnic minorities were more likely than non-Hispanic whites to start psychotherapy rather than medication -- an important reminder that health care providers and organizations need to consider the preferences of patients when developing treatment strategies and recommendations.

"Over the last decade, there has been a growing effort to raise awareness about mental health and to integrate mental health care into primary care," said Waitzfelder. "This is a positive development, since most people receive care from primary care providers. However, our study shows there is a lot more work to do to understand why many depressed patients do not begin treatment."