A new meta-analysis confirms that depression affects twice as many females as males, and this gap appears as early as age 12. The results, published in the journal Psychological Bulletin, are based on existing studies involving more than 3.5 million people in more than 90 countries.
“We found that twice as many women as men were affected,” said co-author Dr. Janet Hyde, a professor of psychology and gender and women’s studies at the University of Wisconsin (UW)-Madison.
“Although this has been known for a couple of decades, it was based on evidence far less compelling than what we used in this meta-analysis. We want to stress that although twice as many women are affected, we don’t want to stereotype this as a women’s disorder. One-third of those affected are men.”
The gender gap was evident in the earliest data studied by co-authors Hyde; Rachel Salk, now a postdoctoral fellow in psychiatry at the University of Pittsburgh School of Medicine; and Dr. Lyn Abramson, a professor of psychology at UW-Madison.
“The gap was already present at age 12, which is earlier than previous studies have found,” Hyde said. “We used to think that the gender difference emerged at 13 to 15 years but the better data we examined has pushed that down to age 12.”
The gender difference tapers off somewhat after adolescence, “which has never been identified, but the depression rate is still close to twice as high for women,” she said.
For the meta-analysis, the researchers looked at both diagnoses of major depression and at symptoms of depression. “Symptoms are based on self-reported measures — for example, ‘I feel blue most of the time’ — that do not necessarily meet the standard for a diagnosis of major depression. To meet the criteria for major depression, the condition must be evaluated much more rigorously.”
The researchers also investigated the link between depression and gender equity in income. Surprisingly, nations with greater gender equity had larger gender differences — meaning women were disproportionately diagnosed with major depression.
“This was something of the opposite of what was expected,” said Hyde. “It may occur because, in more gender-equitable nations, women have more contact with men, and therefore compare themselves to men, who don’t express feelings of depression because it doesn’t fit with the masculine role.”
Puberty, which occurs around age 12 in girls, could explain the early onset.
“Hormonal changes may have something to do with it, but it’s also true that the social environment changes for girls at that age. As they develop in puberty, they face more sexual harassment, but we can’t tell which of these might be responsible,” said Hyde.
Although the data did not cover people younger than 12, “there are processes going on at 11 or 12 that are worth thinking about, and that matters in terms of intervening,” she said.
“We need to start before age 12 if we want to prevent girls from sliding into depression. Depression is often quite treatable. People don’t have to suffer and face increased risk for the many related health problems.”
While the findings covered averages across the world, similar results emerged from the studies focusing on the United States alone. Curiously, no relationship in either direction appeared for depression symptoms.
Despite the prevalence of and growing concern about depression, “this was the first meta-analysis on gender differences in depression,” Hyde said. “For a long while, I wondered why nobody had done this, but once I got into it, I realized it’s because there is too much data, and nobody had the courage to plow through it all. We did, and it took two years.”
Source: University of Wisconsin-Madison