The drive to understand how the brain works, why it malfunctions, and its rates of disease and dysfunction is like assembling a giant puzzle consisting of thousands of pieces. Each new finding signifies a new piece, however small. The more we learn, the closer we come to completing that puzzle and developing more effective mental health treatments.
There are times in the process when a new study calls into question established assumptions, so that what we thought we knew proves to be incomplete or even wrong. For example, scientists have long explained clinical depression in terms of a neurochemical imbalance involving the neurotransmitter serotonin; that was until, in a July 2022 comprehensive review of past studies, researchers at the University of College London found “no evidence that depression is caused by low serotonin levels.”
What Mental Illness Is Much More Common Than Previously Thought?
Another such “aha” moment has forced scientists to revisit the prevalence of at least one mental illness. What many people still don’t know— (and need to know for the sake of their health and that of their loved ones)—is that major depression occurs at much higher rates than they probably thought.
A study by the Yale School of Public Health in July 2020 found that “the number of adults in the United States who suffer from major depressive episodes (MDEs) at some point in their life is far higher than previously believed.” Just how much higher? National surveys have typically pegged the number of women and men who report MDEs at 17 percent and 10 percent, respectively; but, by creating a simulation model, the Yale researchers were able to generate a more accurate estimate of lifetime depression. What they found in the process was that 30 percent of women and 17 percent of men—almost double previous estimates—had had major depressive episodes.
Why Previous Estimates of Major Depression Rates Wrong?
What explains the big discrepancy between the Yale study’s much higher estimated rates of major depression and previous findings? “Recall error,” according to the researchers, as in the natural human tendency to not remember or accurately report personal health histories in surveys.
If recall error led to the lowballing of rates of major depression, it’s not out of the realm of possibility that recall error could have contributed to similar miscalculations regarding the rates of other mental illnesses. What if anxiety disorders, already the most common mental health conditions in the U.S., were in fact twice more common than originally believed to be—for the same reason (that people underreport or forget the symptoms they’ve had)?
Symptoms of a Major Depressive Episode
The fact that major depression is far more common in the U.S. than previously believed means everyone can benefit from knowing its symptoms. The condition is usually very treatable: Many people have found relief with medication and therapy, as well as changes in lifestyle such as diet and exercise. If left untreated, major depressive disorder can be debilitating and life-threatening, however.
Two weeks or longer of these symptoms could indicate a major depressive episode that needs immediate consultation and treatment:
- Feelings of extreme sadness and hopelessness
- Noticeable changes in appetite and weight
- Troubles falling or staying asleep or sleeping excessively and having trouble getting out of bed
- Suicidal thoughts and/or behaviors
The Yale study underlines at least one very important message: The massive scale of mental health issues, especially major depression, in the U.S. and around the world should enlarge research into brain health and treatments and therapies for mental illness. The puzzle is far from complete, but with each new study, we have more of the picture.