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Sleeping next to the baby lowers testosterone levels in fathers
Last reviewed: 01.07.2025
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In our society, the traditional attitude is firmly entrenched: a woman is obliged to raise children, and a man is obliged to be a breadwinner and provide for the family.
However, the father's involvement in the child's development is no less important than the mother's role. Many people believe that the "mother-child" bond is much more important than the "father-child" bond, but this is not true.
A new study by scientists from the University of Notre Dame confirms that the biological connection exists not only between mother and child, but between the baby and father.
The closer the baby and father sleep, the more the father's testosterone levels decrease.
Previous studies of such responses in humans and animals suggest that lowering testosterone levels helps men become more responsive to the needs of their children, allowing them to focus more fully on parenting.
The study involved 362 men with children aged 25-26 years.
All subjects were divided into three groups: the first group slept with their children on the same bed, the second group slept in the same room with the babies, and the third group of fathers and children slept in separate rooms.
All men had their blood testosterone levels measured throughout the experiment.
While awake, all three groups had approximately the same measurement results, but in the evening, before bed, the situation changed somewhat.
Scientists found the lowest level of the hormone in fathers who slept with their children in the same bed, and the highest in those who slept with their babies in different rooms.
"Men are able to respond to children physiologically," says anthropologist Lee Gettler. "Our research shows that when a man becomes a father, the level of testosterone in his blood decreases, sometimes significantly. Those fathers of the family who spend most of their time with their children - feeding them, walking with them and reading stories - have low levels of the hormone.
These new findings add to what is already known, showing that closeness between fathers and children influences men's biology, and their daytime behavior is further evidence of this.
“There are lots of interesting areas for research in this area, such as whether this reflects the role of fathers in our evolutionary past? What differences do fathers have when they are with their children at night? How does a child’s sleep affect the sleep of their parents?” says Professor Getter. “There is often a perception in public discourse that masculinity is solely determined by testosterone, but this is not the case. As we see, what was once considered a female prerogative – raising and caring for children – is not alien to men either, and there is growing evidence for this.”
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