How common is depression? This is one of the fundamental questions Deborah Hasin and colleagues addressed in a recent epidemiological study about Major Depressive Disorder (MDD) in the United States.
The study analyzed data collected in 2012 and 2013 to provide an update on similar research from over a decade ago. Over 36,000 individuals age 18 and older were interviewed by trained personnel as part of the National Epidemiologic Survey on Alcohol and Related Conditions III. The analysis utilized the most current diagnostic criteria found in DSM-5. Participants were evaluated for depressive episodes and other psychiatric conditions that occurred during the previous 12 months as well as over their lifetimes.
Over 10 percent of the individuals in this study experienced function-impairing depression during the previous 12 months, and about 20 percent had experienced depression during their lifetimes. The prevalence was almost twice as high in women compared to men. During the previous year, reported depression was less common in those 65 and older than in those younger than 65. In fact, the prevalence of depression was 5.4 percent in the older group, considerably lower than the average.
About 13 percent of depressive episodes occurred shortly after the death of a loved one and lasted less than two months. In previous years, these episodes would have been diagnosed as bereavement, but the new diagnostic manual has eliminated bereavement as a separate diagnosis.
An interesting subtype of depression, called depression with mixed features, accounted for about 15 percent of the depressive episodes experienced by participants during their lifetimes. Mixed features include symptoms that might be expected in persons with bipolar disorder but do not reach the diagnostic threshold for bipolar I or bipolar II disorders. Among those are expansive or elevated mood, inflated self-esteem, rapid speech, racing thoughts, and increased energy. Thus, some individuals with moderate to severe depression demonstrate brief periods of elevated mood; it is uncertain whether these individuals go on to exhibit a diagnosable form of bipolar disorder.
How many depressed individuals consider suicide? Suicidal thoughts and suicide attempts occur in depressed persons. In this study, 39 percent of people with a history of depression had “thought a lot about suicide” and more than 13 percent had attempted suicide.
On average, how long do depressive episodes last? It has become increasingly clear that depression can be a chronic illness for some people. Results from this study indicate that during their lifetimes, 44 percent of individuals experienced episodes that lasted a year or longer and 30 percent had episodes lasting two years or longer.
Are other psychiatric illnesses associated with depression? The investigators found that co-morbid substance use disorders, anxiety disorders, and borderline personality disorder were common in persons with depression. Fifty-eight percent of people with lifetime major depressive disorder had a substance abuse disorder during their lifetime (including alcohol and nicotine use disorders as well as other drug use disorders), 37 percent an anxiety disorder, and 27 percent borderline personality disorder.
How many depressed individuals receive treatment? Interestingly, almost 70 percent of those who had experienced depression at some point during their lifetimes had received treatment. More than 50 percent had received medications and more than 60 percent had received counseling from a professional therapist. The percentages were lower for those who had experienced depression during the previous 12 months: about 50 percent had received some sort of treatment, 37 percent with medications and 44 percent with professional talk therapy. The intensity of treatment was not defined, however, and other research suggests that many who receive treatment do not receive adequate amounts of it.
The rates of depression found in this recent study are at least 50 percent higher than rates from the study performed a decade earlier. Whether this increase is a result of methodological differences or reflects a true increase in the prevalence of the illness is unclear. However, the authors point out that an increase in prevalence is supported by other studies demonstrating increases in indicators of depression and suicidality. Even if some of the observed increase is related to differences in methodology, it appears that an increasing number of people are suffering from this disorder.
Depression is one of the most disabling of all illnesses. We must do more to understand its various causes in order to develop better strategies for prevention and treatment.
This article was written by Eugene Rubin M.D., Ph.D. and Charles Zorumski M.D.