University of Canterbury PhD candidate Jacqueline Tither (Psychology) says that her study employed a unique within-family design to account for pre-existing factors such as genetic and socioeconomic differences too.
She compared 68 pairs of sisters from father-absent homes with 93 pairs of sisters from father-present homes in New Zealand. The sisters in each pair were full biological siblings who were at least two years apart in age. In the father-absent families, the biological parents had split up prior to the younger sister's getting her first period.
Tither found that common processes such as separation, divorce and departure of the father from the home can substantially alter pubertal timing in girls.
Such was not the case in father-present families.
"Importantly, the current study indicates that absent fathers are not created equal, and the impact of father absence on pubertal timing is more nuanced than previous research suggests," Tither said.
The study revealed that it was the younger daughters of the most dysfunctional fathers who were most likely to experience the earliest pubertal timing. Specifically, younger sisters with the most dysfunctional absent fathers got their first period 11 months earlier than their older sisters. The younger sisters from father-absent, but not seriously dysfunctional families, did not get affected that way.
The findings will be published this month in the Developmental Psychology Journal
Tither believes that the stress associated with living with a very dysfunctional father, and the removal of this stress when he lefts the family home, might have substantially accelerated pubertal development in daughters, providing the father departed early enough.
As for the older sisters, the stress might have been removed too late for them to also experience early menarche. They had spent longer time with the dysfunctional fathers after all. Hence perhaps more used to it all, Tither postulates.
She now intends to test for possible mediating mechanisms that may account for this divergent pattern of sexual maturation in older and younger sisters.
"Given that early pubertal maturation in girls is associated with a variety of negative health and psychosocial outcomes - such as mood disorders, substance abuse, adolescent pregnancy, and a variety of cancers of the reproductive system - it is important that risk factors for early puberty are identified," she says.