Sleep-Onset Association Disorder
Sleep-onset association disorder occurs when your child associates or closely connects his ability to fall asleep with "something in the environment" (such as being held by his parent; being rocked to sleep; nursing, drinking, or eating at bedtime; watching television or even sleeping in a parent's or sibling's bed). When this "something in the environment" is absent, your child cannot fall asleep. All of us wake up briefly a number of times each night, but we are usually not aware that we wake up because we fall back asleep very quickly. For children with sleep-onset association disorder, when they awake during the night, they are not able to fall back asleep if their "something in the environment" is not present. If your child is only able to nap or fall asleep at night in the car (or in one bed but not another), he likely has a sleep-onset association problem.
Nighttime Eating / Drinking Disorder
Nighttime eating / drinking disorder is more common among infants and toddlers and involves "excessive" nighttime feeding (often nursing or bottle-feeding) that is required for the child to fall asleep or return to sleep. For infants, feeding during the night is a normal part of development. However, by the age of 5 or 6 months, most children are not drinking more than 8 ounces of fluid during the night (or nursing more than once or twice).
Limit-Setting Sleep Disorder
Limit-setting sleep disorder is more common for children who are fully ambulatory (i.e., able to walk / run) and have developed receptive and expressive language skills (typically after age 2). Limit-setting problems are characterized by a child refusing or stalling bedtime (e.g., "I need to go to the bathroom, get a drink of water, one more hug, tell you something really really important, etc.) and making it hard for the parent to leave the child's room without them getting up out of bed. Attempts to have the child return to bed may result in behavioral outbursts (e.g., crying; screaming; destruction of property or aggression).