Mothers who were still co-sleeping -- sharing either a room or bed -- with their infants after six months were more likely to feel depressed, finds a study.

This was a result of recent trends and popular advice telling mothers not to sleep with their babies. Thus, those who do choose to co-sleep with their infants tend to be worried about their babies' sleep and think their decisions were being criticised. According to the study, mothers that were still co-sleeping after six months reportedly felt 76 per cent more depressed than mothers who had moved their baby into a separate room.

In addition, these mothers were also 16 per cent more criticised or judged for their sleep habits. "We definitely saw that the persistent co-sleepers -- the moms that were still co-sleeping after six months -- were the ones who seemed to get the most criticism," said Douglas Teti, Professor at the Pennsylvania State University.

"Additionally, they also reported greater levels of worry about their baby's sleep, which makes sense when you're getting criticized about something that people are saying you shouldn't be doing, that raises self-doubt. That's not good for anyone," Teti added. In the study, published in the journal Infant and Child Development, the researchers garnered concerns about sudden infant death syndrome (SIDS) or the desire for babies to learn how to fall asleep on their own are some of the reasons why parents should prefer their babies to be sleeping alone.

Researchers analysed the sleeping habits of 103 mothers in their baby's first year of life. "We found that about 73 per acent of families co-slept at the one-month point. That dropped to about 50 per acent by three months, and by six months, it was down to about 25 per cent," Teti said. "Most babies that were in co-sleeping arrangements in the beginning were moved out into solitary sleep by six months." Moreover, even when co-sleeping works well, it can still cause more loss of sleep for the parents than if the baby slept in its own room.

"Co-sleeping, as long as its 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," Teti said. Teti said that it is not about whether co-sleeping is good or bad, but about the importance of finding a sleep arrangement that works well while not neglecting your partner or spouse. "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," Teti noted.