Prevalence, Treatment, and Control of Depressive Symptoms in the United States: Results from the National Health and Nutrition Examination Survey (NHANES), 2005–2008

Ruth S. Shim, MD, MPH; Peter Baltrus, PhD; Jiali Ye, PhD; George Rust, MD, MPH


J Am Board Fam Med. 2011;24(1):33-38. 

In This Article



The NHANES is designed to assess the health and nutritional status of Americans by combining interviews and physical examinations.[15] The surveys have been conducted annually by the National Center for Health Statistics since 1999, using a complex multistage sampling design to obtain a representative sample of the civilian, noninstitutionalized population of the United States. The NHANES oversamples minorities and allows for population estimates using population totals from the Current Population Surveys. To obtain an adequate sample size for the analyses we combined the data from the 2005 to 2006 and 2007 to 2008 NHANES, for a potential total sample size of 11, 791 adults aged 18 and older.


Depressive symptoms were assessed using the PHQ-9, a 9-item screening tool that asks participants to choose 1 of 4 responses about the frequency of depressive symptoms during the previous 2 weeks.[14] Those scoring ≥10 were characterized as having moderate, moderately severe, or severe depressive symptoms.

Antidepressant use was defined as taking at least one prescribed antidepressant medication in the past 30 days, as characterized by the Multum Lexicon Drug Database.[16] During the household interview, survey participants were asked if they had taken a medication in the past month for which they needed a prescription. Those who answered "yes" were asked to show the interviewer the medication containers of all the medications used.

Although the NHANES does not provide details on psychological counseling, we defined counseling and various types of therapy as treatment with a mental health professional, which was measured by the survey question, "During the past 12 months, have you seen or talked to a mental health professional such as a psychologist, psychiatrist, psychiatric nurse, or clinical social worker about your health?"

Because evidenced-based treatment recommendations for prescribing antidepressant medication and/or administering psychotherapy exist for individuals with PHQ-9 scores >15, we specifically examined all forms of treatment among respondents that scored >15 on the PHQ-9. Evidence-based treatment recommendations for individuals with a PHQ-9 score <10 involve a strategy of watchful waiting and reassessment for antidepressant treatment or psychotherapy after 2 months.[17]

Statistical Analysis

Frequencies, population estimates, standard errors, and 95% CIs taking into account the complex sampling design and population weights were generated by Proc Crosstabs in SAS-callable SUDAAN version 9 (Research Triangle Institute, Research Triangle Park, NC). First, overall prevalence of depressive symptoms and prevalence of the different depressive symptom severity categories were assessed for the entire adult population. Treatment (mental health professional and/or antidepressant) use by depressive symptom severity was then assessed. Prevalence of depressive symptoms, depressive symptom severity, and treatment among different age-sex groups was also examined.


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