The reliable one, the fixer, the one everyone calls: a new lens on a very familiar role. You remember the school pickups for your younger siblings, the dinners you helped make, the arguments you calmed before your parents got home. Maybe you still get the first call when something goes wrong in the family. If you are an eldest daughter, none of this sounds unusual. It just sounds like your life.
Online, this experience now has a name: eldest daughter syndrome. It is not a clinical diagnosis, but it describes a familiar pattern of first-born girls who took on childcare and household work early, and who often still feel strongly responsible for their family’s well-being. Now UCLA anthropologist Molly Fox and her colleagues have asked a surprising question: could part of that role begin even before birth?
What the UCLA Study Found
In a study published in the journal Psychoneuroendocrinology in February 2024, Fox and researchers from UC Irvine, UC Merced, Chapman University and the University of Denver followed 253 mother-child pairs for 15 years. The mothers were recruited early in pregnancy at two obstetric clinics in Southern California. Their stress, anxiety and depression were measured five times during pregnancy, and their children’s puberty was tracked at ages 8 to 10, 11 to 12 and 13 to 16, including through hormone levels in saliva.
The result: when mothers reported more distress during pregnancy, their first-born daughters showed earlier signs of adrenal puberty. The same pattern did not appear in boys or in daughters who were not first-born. “This is a first-of-its-kind finding and is fascinating to look at through an evolutionary lens,” Fox said.
Adrenal Puberty, Explained
Puberty happens in stages. Adrenal puberty involves changes such as body hair growth, pimples and aspects of cognitive maturation. It is separate from the stage that brings breast development and a first period, and the study found no comparable effect on that later stage.
That detail matters for Fox’s interpretation. She has suggested that early adrenal maturation, without early menstruation, may help a first-born daughter support her mother in raising younger children: mature enough to help, but not yet starting a family of her own. It is a proposed explanation, not a proven one, and the study shows a correlation, not cause and effect.
If You Were the Family’s Second Parent
Whatever its origins, the role can be heavy. Start by naming it: notice when you step in automatically to fix, plan or soothe. Ask yourself whether the task is really yours, or simply familiar. Let a sibling take the lead on the next family decision, even if they do it differently. Practice asking for help yourself, out loud. And give your younger self some credit: that early responsibility built real skills, from organizing to empathy, that you can now use on your own terms.
Being the dependable one often comes from a generous place. Psychologists have found that adults over 55 often help more when it is hard. Quiet habits can also help you slow down, like walking with your hands behind your back, a gesture psychologists link to reflection and calm. The lesson worth borrowing is that being reliable is a strength, as long as you are not the only one being relied on.
The Bottom Line
Many women who grew up as the eldest daughter became the family’s second parent. A 15-year UCLA study suggests the role may have roots before birth: first-born daughters of mothers who felt more distress during pregnancy showed earlier signs of adrenal puberty, a pattern not seen in boys or later-born girls.
