Many children are overwhelmed with feelings of longing for an absent parent, and this can have strong physiological effects. A new study now shows that the father’s absence before birth and during childhood may be associated with earlier onset of puberty, especially for girls. Since other research shows that earlier puberty is associated with an increased risk of depression, obesity and some types of cancer later in life, the researchers think that this should be investigated further.
Girls in the early 19th century began to menstruate at 17 years on average, but this declined to about 13 years by the mid-20th century. Girls’ age at the onset of puberty has continued to drop in the past 25 years, although the rate of decline has slowed. Earlier puberty is associated with mental disorders such as depression and anxiety in adolescence and cardiovascular disease and some types of cancer in adulthood, and researchers are therefore seeking to find the causes. The largest study to date quantifies a 40-year-old theory – that the absence of a father influences the onset of puberty.
“The pattern is clear for girls. If the father was absent from before birth, girls started puberty on average 3 months earlier, and this difference declined in accordance with the girl’s age when the father left the family during childhood. For boys, the trend was only present if the father was absent from late childhood (6–10 years old). We do not yet know why this association exists, but there are various theories some of which, we investigated in our study. Future research should also investigate other theories, such as how differences in type of family affect the age of onset of puberty, but for now we should at least pay special attention to the children of divorced parents – both their well-being and physical health,” explains Anne Gaml‐Sørensen, PhD student, Department of Public Health, Aarhus University.
Very obvious effect
The data come from 92,000 pregnant women and their children participating in the Danish National Birth Cohort. The study collected data from almost 16,000 of the children born in 2000–2003 to investigate the relationship between the absence of the father during pregnancy and in childhood and the onset of puberty among girls and boys (families headed by a father were excluded).
We followed the children from age 11 years and through puberty to determine when they reached various stages, such as menstruation, breast and pubic hair development. A combined puberty marker for the girls showed that the absence of the father during pregnancy and in childhood was associated with earlier pubertal development. If the mother did not live with the father before the birth, the daughters entered puberty on average 3 months earlier.
If the father moved away from the family in early childhood (child 0–5 years old), puberty began about 2 months earlier, and the absence of the father in late childhood was only associated with 1 month earlier pubertal development. They adjusted for several measures of social status, the mother’s age at first menstruation as a genetic marker and other maternal lifestyle factors that could influence the children’s age at the onset of puberty.
“The researchers did not find as clear a trend among boys, only an association with the absence of the father in late childhood. Since only a few studies have investigated the age at onset of puberty among boys following father absence, this finding should be investigated further. Traditionally, not much research has focused on boys’ pubertal development because a measurable pubertal marker such as menstruation is lacking among boys,” says co-author Cecilia Ramlau-Hansen, Professor, Department of Public Health, Aarhus University.
Adjusting for stress and BMI
Although clear data showing the possible effect of the absence of the father have first become available now, since the 1980s there have been many indications of and theories about how the absence of the father could affect whether children have earlier onset of puberty, especially daughters.
“The earliest theories indicated that early childhood is a sensitive period in which the absence of the father can influence daughters to engage in earlier sexual activity and sons more stereotypical masculine behaviour. Later theories suggested that stress in early childhood affects children’s onset of puberty,” says Anne Gaml-Sørensen.
Researchers have also suggested that because divorced parents are busy, their children on average eat more calorie-dense food and have a higher body mass index (BMI). This was thought to affect hormones and thus the onset of puberty, but the results do not support this theory.
“We examined this theory using our data, but we found the same correlation between the absence of the father and earlier puberty regardless of considering whether the father spent a lot of time with the child at 1.5 years; the degree of stress and well-being in childhood; and the childhood BMI,” explains Anne Gaml-Sørensen.
The quality of absent fathers
Another theory suggests that the effect is genetic, assuming that fathers with a greater tendency to divorce have a higher expression of specific hormone receptors, which are passed on to the daughter so that she menstruates earlier. However, several studies are needed to determine whether the cause is genetic or environmental.
“Measuring the quality of a father who is not there is incredibly difficult, and we could only determine whether the father lived with the mother and the child at various times in childhood. Perhaps the absence of the father is not crucial but lack of a parent is, although some studies do not find the same association between the absence of the mother and earlier puberty,” says Anne Gaml‐Sørensen.
The family might also experience stress in connection with the divorce that explains the association, although this is difficult to quantify.
“We hope to investigate different types of family and determine whether the effects are similar. By examining the children of self-selected single parents and homosexual couples, we may be able to uncover and rule out some of the many possible effects,” concludes Anne Gaml‐Sørensen.