JAMA Depression Issue Highlights Reasons for Concern

In the lead article in the JAMA theme issue, Ronald Kessler, Ph.D., a professor of health care policy at Harvard Medical School, and his colleagues report results from the National Comorbidity Survey Replication (NCS-R). The NCS-R surveyed more than 9,000 adults in a nationally representative sample between February 2001 and December 2002 to “update information on the prevalence, correlates, and clinical significance of DSM-IV disorders,” the authors wrote, as well as to study patterns and correlates of treatment and treatment adequacy.

This report provides data on the NCS-R estimate of the prevalence of major depressive disorder, while future reports are expected to be released on other disorders. The researchers found that 16.2 percent of adults in the U.S.—representing over 32 million persons—have experienced a major depression at some time in their lives, and 6.6 percent of all U.S. adults—representing just over 14 million persons—have experienced depression within the 12 months preceding the survey.

“This survey represents the largest population sample of U.S. adults—representative of all 48 contiguous states—and includes a much broader range of ages, from 12 to 94 actually, than any prior study,” said Kathleen Ries Merikangas, Ph.D., co-principal investigator with Kessler on the study and senior investigator and chief of the Section on Developmental Genetic Epidemiology at the National Institute of Mental Health. (Only data from subjects aged 18 and older were included in the final analysis.)

“We strictly adhered to DSM-IV criteria,” Merikangas told reporters during the press briefing, “and, importantly, included clinical follow-up on a significant proportion of those originally surveyed in their homes.”

The survey interviewed individuals in their homes using laptop computer–based editions of the World Health Organization’s Composite International Diagnostic Interview (CIDI), enhanced to avoid an overdiagnosis of clinically nonsignificant depressive symptoms previously associated with the CIDI. The enhancements, the authors reported, “specifically probed for severity of dysphoria and anhedonia, by requiring clinically significant distress or impairment associated with these symptoms, and by asking separate questions about symptom duration (hours per day, days per week, and duration of depressive episodes).”

“For those individuals whose CIDI indicated major depression,” Merikangas said, “a clinician followed up with them and conducted a full Structured Clinical Interview for DSM-IV.” A corresponding group without major depression on the CIDI was also given the SCID as a control measure. The severity of the depression and the amount of disability involved were evaluated using the Quick Inventory of Depressive Symptomatology and the WHO Disability Assessment Schedule, as well as the Sheehan Disability Scale.

The survey revealed significant trends toward higher rates of depression in specific demographic groups.

Depression was most prevalent in younger individuals for both men and women, although women had significantly higher rates at all ages.

“We think these are real trends,” Merikangas told reporters, “and not an artifact of either the reporting process or other methodology. And the trends are important. They really tell us, for example, where we need to focus our assessment and treatment efforts.”

Lifetime prevalence of depression was significantly elevated not only in younger age groups, but in women who were classified as “other” with regard to employment, which Merikangas clarified generally meant they were unemployed. The 12-month prevalence rates were significantly higher in younger women—those 18 to 29 were three times as likely and those 30 to 44 were 1.8 times as likely as those age 60 and older to be depressed—and were more likely to be Hispanic, a homemaker, student, or unemployed; had never married; and did not finish high school. In addition, those living below the poverty level were 3.8 times as likely to be depressed compared with those who were financially stable (living at three times the poverty level or above).

The current study also confirmed reports that depression is highly comorbid. Nearly three-quarters of those with lifetime depression (72 percent) and two-thirds of those with depression in the previous 12 months (64 percent) also met criteria for at least one other DSM-IV disorder, most commonly an anxiety disorder, impulse control disorder, or substance abuse.

“We also confirmed that major depression involves clinically significant distress, role impairment, and high clinical severity and is persistent,” Merikangas emphasized. “This disorder claims on average 16 weeks per year from people’s lives on a recurring basis. Over their lifetime, that adds up to 10 years lost to this debilitating disorder.”

The survey found that of those with depression in the previous 12 months, 97 percent reported at least some impairment, with 87 percent noting the impairment as “at least moderate,” 59 percent as either severe or very severe, and 19 percent as very severe. Impairment was greatest in social roles and lesser in work roles, although those with depression in the previous 12 months reported an average of 35 days in the past year in which they were totally unable to work or carry out their normal activities (see article at top of facing page).

The survey also noted significant increases in the proportion of persons with depression in the previous 12 months who received treatment for their depression, compared with the findings of earlier studies. The original National Comorbidity Survey (NCS), conducted in 1990 to 1992, indicated that 36 percent of those with depression in the previous 12 months had received some form of treatment. In the current report of the NCS-R, more than half (57.3 percent) received some treatment in the preceding year, although only 42 percent of those received adequate treatment. “Minimally adequate treatment” was defined using APA’s Practice Guideline for the Treatment of Patients With Major Depression and the Agency for Health Care Quality criteria and included either “a minimum of four visits with a physician for pharmacotherapy that included the use of an antidepressant or mood stabilizer for at least 30 days, or at least eight outpatient visits with any professional in the specialty mental health sector.”

The specialty mental health sector was defined in the study as “inpatient treatment or outpatient treatment with a psychiatrist, psychologist, any other mental health professional, or a social worker or counselor in a mental health specialty setting or use of a hotline.”

Merikangas noted that analysis of all of the data continues, and the researchers hope to further break down specific trends in how depression affects different groups of people.

“These results represent obvious advances as far as getting better information on disability and severity of mental disorder diagnoses,” commented Darrel Regier, M.D., M.P.H., executive director of the American Psychiatric Institute for Research and Education and director of APA’s Division of Research.

Regier, along with William Narrow, M.D., M.P.H., associate director for diagnosis and classification in APA’s Division of Research, last year published revised prevalence estimates for psychiatric disorders, including depression. That report, which appeared in the February 2002 issue of Archives of General Psychiatry, established clinical significance of disorders in the community as a crucial factor in estimation of treatment needs (Psychiatric News, April 5, 2002).

Regier and Narrow aimed to reconcile earlier estimates of disorder prevalence from the Epidemiologic Catchment Area (ECA) Program and the original NCS. The ECA had estimated the prevalence of major depression in the previous 12 months for adults aged 18 to 54 at 5.4 percent, and the NCS estimate was 8.9 percent. The revised estimate, taking into account clinical significance criteria, placed the one-year prevalence of major depression at 4 percent.

While the current study’s one-year rate of 6.6 percent is higher, Regier noted that each of the three studies employed different methodologies on different populations.

“It’s hard to know what is really happening with these rates,” Regier said, “without a clear understanding of the instrument changes and the age groups under consideration.”