Do you do co-sleeping? Why?

Anthropologists observed that all mammals and primates, as well as the majority of non-Western societies around the world, coslept. Therefore, it was likely that the practice had some biological advantage.

One of McKenna and his colleagues’ greatest scientific contributions has been to show how parents serve as a kind of biological “jumper cable,” to a newborn baby when she is completing her gestation outside her mother’s body. When parents and babies sleep together, their heart rates, brain waves, sleep states, oxygen levels, temperature, and breathing influence one another.

To a biological anthropologist, this mutual influence implies that the offspring’s growth is intended to occur most safely inside that biological system, near an adult’s body, especially in the first few months of life while the baby’s own physiology is the most immature.

For example, animal studies found that when baby monkeys were separated from their mothers, their bodies went into severe stress. A small study of 25 four- to ten-month-old babies who were separated for sleep training showed that even though the babies’ behavior quieted on the third night, their levels of cortisol (a stress hormone) remained high.

At the same time, both adults and babies sleep longer overall when they bedshare, probably because caregivers don’t have to get all the way up out of bed to feed and babies don’t have to call out, wait for help, and settle back down. And that longer sleep has implications for parent-child interactions in the daytime. Research suggests that more well-rested parents make better decisions and, importantly, have better emotion regulation. Sleep deprivation also raises the risk of postpartum depression.

Fathers who bedshare benefit in other ways, too: One study found that when fathers slept close to their babies, their testosterone dropped more compared to fathers who slept separately. Men with lower testosterone tend to engage in more sensitive and responsive parenting, which means that bedsharing may make for better fathering.

When not to co-sleep

Co-sleeping always increases the risk of SUDI including SIDS and fatal sleeping accidents. Co-sleeping increases this risk even more if:

• you’re very tired or you’re unwell
• you or your partner uses drugs, alcohol or any type of sedative medication that causes heavy sleep
• you or your partner is a smoker
• your baby is unwell
• your baby is less than three months old, or was premature or smaller than most babies at birth.
  You should never sleep together with your baby if any of the above points apply to you or your partner.