The eldest daughter is often the one who seems able to handle everything. Psychologists say that for some women, that competence has a hidden cost: they learned as children that being responsible for everyone else came before having needs of their own.

Adult daughter sitting with her mother on a sofa while they use a laptop

She remembers the birthdays, notices when a parent’s voice changes, checks whether the younger siblings got home, and arrives at a crisis with a plan. The eldest daughter is often described as...