Waking to eat is normal, not a sign of fighting sleep
One of the most concrete reasons babies resist sleep is that they wake up hungry. In a Swedish population study of infants, a common pattern was that the baby wakes up to eat and most often goes back to sleep afterward [3]. That means the resistance is often not a refusal of sleep itself but a need that interrupts it.
Frequent night waking is common in the first year. In one study, when children were 8 months old, 10% of mothers reported their babies woke three or more times per night [1]. That number matters because it shows that repeated waking is a widespread infant pattern, not an unusual failure.
Parental anxiety and depression can keep sleep problems going
Sleep difficulties in babies do not sit in isolation from the adults caring for them. Research on severe sleep problems in infants has examined correlates such as parental anxiety and feeding behaviors [3]. Another study of sleep problems in early childhood reported that factors like maternal depression may contribute to persistent sleep difficulties [1].
These findings are about associations, not proof of a single cause. They suggest that a baby's sleep struggle can be entangled with a parent's emotional state, which may shape how sleep is managed and how persistent the problem becomes [1][3].
Whether a baby is "fighting sleep" depends on the parent's experience
A baby's sleep behavior only becomes a "problem" in a particular context. One review argues that the most useful definition of an infant sleep problem is the parent's experience — that is, whether the parent finds the baby's sleep difficult [5]. The same waking pattern can feel manageable to one family and exhausting to another.
That framing helps explain why advice about fighting sleep varies so much. Structured questioning about the details of a baby's sleep has been used to break the deadlock between parent and baby over sleep [4]. The practical target is often the fit between the baby's pattern and the family's routine, not a single underlying defect in the baby.
The sleep setting shapes how sleep goes
The environment a baby sleeps in is part of the picture. A review of babies and their sleep environment examined factors that influence the choice of sleep settings and asked whether a relation exists between those environments and later sleep problems [2]. It also reviewed sleep-wake state physiology and offered recommendations for optimal sleep settings [2].
This does not establish that a particular room or routine causes a baby to fight sleep. It does mean that where and how a baby is put down is a relevant variable, alongside hunger and parental state, when trying to understand why settling is hard [2].
Sources used in this answer
Sleep problems in early childhood: continuities, predictive factors, and behavioral correlates
At 8 months old, 10% of mothers reported their babies woke three or more times per night, and factors such as maternal depression may contribute to persistent sleep difficulties.
Babies and their sleep environment
The review examines factors influencing babies' sleep environments and whether sleep settings relate to subsequent sleep problems, without addressing why babies resist sleep.
Severe sleep problems among infants in a normal population in Sweden: prevalence, severity and correlates
In a Swedish infant population, severe sleep problems were studied for prevalence and correlates including parental anxiety and feeding, with a common pattern being that the baby wakes to eat and then goes back to sleep.
Sleep problems in babies and young children
Structured questioning about the details of a baby's sleep can help break the deadlock between parent and baby over sleeping problems.
Sleeping like a baby? Infant sleep: Impact on caregivers and current controversies
The most useful definition of an infant sleep problem may be the parent's experience, that is, whether the parent finds the baby's sleep difficult.