In past studies, pediatricians have often discussed the effects of co-sleeping on infants. But researchers from Penn State are now shedding light on how co-sleeping can affect mothers, linking distress over social criticism with infant sleeping arrangements.

After analyzing sleeping patterns during the first year of motherhood, the study revealed a higher risk of depression and worry in mothers who continued sharing a bed or a room with their babies beyond six months. These mothers also showed a pattern of "lower income, reported greater space constraints; were younger, single, or unemployed; were less likely to have a Bachelor's degree; and were more likely to have infants with greater negative affectivity or problematic night waking."

The study stated that the reported characteristics were most applicable to European-American families. It was suggested that co-sleeping mothers were likely to feel judged due to recent trends encouraging solitary sleep for babies who have crossed six months of age.

Douglas Teti, department head and professor of human development and family studies at Penn State, added that the mother's sleep was more likely to be disrupted during co-sleeping than the father's. He went on to draw attention to cultural differences when it comes to attitudes around co-sleeping. 

"In other parts of the world, co-sleeping is considered normal, while here in the U.S., it tends to be frowned upon," explained Teti, one of the authors of the study. "Co-sleeping, as long as it is done safely, is fine as long as both parents are on board with it. If it's working for everyone, and everyone is okay with it, then co-sleeping is a perfectly acceptable option."

The practice is known to be common in Asian and South American countries. But it's not always a matter of choice for low-income groups who may not have enough rooms or beds in their homes.

Last year, Iowa State professor Susan Stewart published a book sharing the results of her study around the phenomenon. It was revealed that a lot of parents experienced shame and stigma, even refusing to bring up the subject of co-sleeping with family members or doctors. Others found that they slept better when the whole family shared the same room or bed.

“Parents are exhausted, they’re stressed and honestly, it’s often easier to co-sleep,” Stewart said. “There’s no one size fits all, and in my view, there is no right or wrong.”

Teti mentioned that the published study is not taking a side for or against co-sleeping, but seeks to encourage parents to not neglect their own relationship and health. "So this is something to be careful with if you're not good with chronic sleep debt. Co-sleeping needs to work well for everyone, and that includes getting adequate sleep. To be the best parent you can be, you have to take care of yourself, and your child benefits as a result," he said.

Mina Shimizu, a post-doctoral fellow at Auburn University who received her doctorate in human development and family studies at Penn State, also worked on this study.