Long-term co-sleeping with baby can be a sign of family problems

Unique study, filming in bedroom, finds no evidence that co-sleeping with infants causes problems, but suggests difficulties in a couple’s relationship.

Western families where parents continue to sleep with their babies after six months are more likely to experience relationship difficulties, poor co-parenting and maternal depression, according to unique observations inside the bedroom.

We found no evidence that ‘co-sleeping’ past six months is a problem in itself. However, our findings suggest that, at least in Western culture, sharing a room or bed long-term with a baby can be a sign of family dysfunction. That is, problematic co-parenting and poor spousal relationships may encourage mothers to share a bed or a room with their babies long-term.

“Those who persisted with co-sleeping beyond six months tended to have higher levels of family problems: marital adjustment and co-parenting. The level of family chaos was higher, and the quality of care putting their baby to bed was lower. Overall, parents were less sensitive.” 

These findings spring from an extraordinary study in which 140 US families allowed cameras to film their bedrooms for a single night at five points during their babies’ first year – during the first, third, sixth, ninth, and twelfth month of the child’s life. The filming was unique. Previous studies have focused a single camera, without sound, on the baby. Our four cameras, with sound, tracked interactions between the parents and the baby as well as between mom and dad.

In some cases, mom and dad operated well together. We could see the baby being put to bed. When mom and dad were well organized, babies would go to sleep and often sleep all night, especially as the infant matured. In other cases, parents didn’t work well together. Sometimes there was disorganisation and there were signs of maternal depression. Some babies faced multiple stressors and often did not sleep well.

Majority co-sleep but switch baby to separate room by six months

We found that 75 per cent of couples engaged in ‘co-sleeping’ – sharing a bed or a room with their babies – during the first few months of life. By six months, however, most had switched their baby to a separate room. The remainder tended to co-sleep for the rest of the year-long study.

Those who persisted with co-sleeping beyond six months tended to have more family problems. Marital adjustment – how well the parents got along – was worse. The quality of co-parenting – how effectively the parents made decisions about the baby together – was poorer. The level of family chaos – how well parents stayed focused on baby-related tasks – was higher, and the quality of care when putting their baby to bed was lower. Long-term co-sleeping parents tended to be less responsive to their babies and to make more hostile comments to their infants. Overall, they were less sensitive to their babies.

Such families, then, typically weren’t functioning as well as families that either placed their baby on its own from the beginning or moved their baby to sleeping alone within six months. We also observed that the differences in family functioning between the persistent and non-persistent co-sleepers showed up as early as when the child reached one month of age—long before it became clear which of the co-sleeping parents would, in fact, carry on past six months. Thus we lean toward the conclusion that problems in family functioning often explain the co-sleeping rather than the other way around.

Family dysfunction link to co-sleeping supported by previous studies

Previous findings add support to our view that persistent co-sleeping could be an outcome or product of family dysfunction. In a 2015 paper, our team found that when mothers reported poor co-parenting and poor spousal relationships at one month, they were much more likely to be co-sleeping with their infants at six months. Additionally, within this particular group of persistent co-sleepers, the mothers were more likely to show symptoms of depression by the time the baby was six months old.

“If parents wish to co-sleep with their infants, it is important to retain a sound balance and to pay plenty of attention to the quality of their partner relationship. Every parent would be wise to care as much for their relationship with their spouse as they do for their relationship with their baby.”

Our conclusion is also consistent with our work from 2012, when we looked into the long-established link between maternal depressive symptoms and babies waking more in the night. Our cameras found an explanation: mothers with elevated depressive symptoms tended to wake their babies up, or go to them when the babies were sound asleep or when they were awake but not distressed. So they were keeping their babies awake. We didn’t see this waking behavior in moms with good co-parenting and spousal relationships who co-slept with their babies at one month.

What’s the picture that emerges from all of these studies? First, poor co-parenting and poor spousal relationships seem to lead to persistent co-sleeping and to raised depressive symptoms in the mothers. Second, mothers with depressive symptoms keep their babies awake more. It may be that, in some cases, problems in the couple relationship lead to heightened stress and, hence, to moms spending more time with their babies at night.

No evidence that co-sleeping is a problem in itself

These findings don’t identify persistent co-sleeping as problematic in itself. Often parents who co-sleep operate healthily and function well as couples and as parents. But our studies indicate that the family system’s health can play a big part in determining how parents structure infants’ sleep in the long term. Sleeping arrangements are not just a function of culture.

Our findings add to accumulating evidence that healthy family functioning lies at the heart of good parenting – good couple relationships and strong co-parenting must be nurtured. Thus we need to help couples maintain the quality of their relationships right from their decision to start a family.

Our findings shouldn’t be interpreted as finding fault with or attacking co-sleeping. I have three children, and I co-slept with all of them. We should advise parents that, if they wish to co-sleep with their infants, they should retain a sound balance and pay plenty of attention to the quality of their partner relationship. Every parent would be wise to care as much for their relationship with their spouse as they do for their relationship with their baby.