Sleep problems in young children and babies are common and can cause stress and tension in the family as the parents become sleep deprived.
Researchers have now found that mothers who are depressed may cause sleep problems in their babies or make them worse, rather than the other way round.
This was because their anxiety and worry led them to disturb their babies when they were sleeping by picking them up and feeding them instead of letting them go back to sleep, taking them into their own bed or cuddling them at night because they needed the emotional comfort rather than their baby.
Lead author Douglas Teti, professor of human development, psychology, and paediatrics at the Pennsylvania State University, said: "This study provides insights about maternal depression's effects on night-time parenting, and how such parenting affects infant sleep."
The research was carried out at the Pennsylvania State University and is published in the journal Child Development.
In the study, mothers with higher levels of symptoms of depression and more worries about their children's sleep had children whose sleep was more disrupted.
After studying 45 mothers and their babies, aged from between one month to two years, over the course of a week, the team found that the mothers with more symptoms of depression were more likely to pick up their babies when they were sleeping or disrupt their sleep in other ways.
The mothers were asked to keep sleep diaries, were interviewed by the researchers during home visits and were video recorded during one night.
The authors suggested that mothers who worry excessively about their babies' wellbeing at night were quicker to respond to slight sounds the baby made even if the infant was not upset or in need of attention.
Alternatively they moved the babies into their own beds because they were worried they needed feeding or if they were comfortable.
The researchers also suggested that depressed mothers might cuddle their infants in the night because they needed the emotional comfort of it instead of only responding when their babies needed settling.
The research paper said: "Although most mothers implemented a calming bedtime routine, ignored non-distressed vocalisations, and had children who sleep through the night (aside from expected night feedings for younger infants), mothers reporting more depressive symptoms displayed much more variability in nighttime interactions with their infants, intervened with their infants when there did not appear to a clear need for intervention (e.g., going to the infant when the infant was awake but not distressed, or when the infant was sound asleep), and had difficulty setting limits with their infants during bedtime and at night."
Prof Teti said: "Although we found greater support for mothers' behaviour explaining the relationship between depressive symptoms and infant night wakings, it's likely that both infants and parents influence infant sleep.
"This helps us better understand what factors influence infants' sleep in homes in which mothers are depressed.
"Sleep problems often endure beyond early childhood and can have a negative effect on various aspects of development, including emotional, behavioural, and academic functioning.
"Understanding how maternal depression and sleep problems combine to affect children's development is important to developing interventions to help reduce these negative consequences."