Children who nap beyond the age of two are more likely to have problems sleeping through the night, Australian research suggests.
A study found that daytime napping led to toddlers taking longer to fall asleep in the evening along with reduced sleep quality and duration.
Early childhood is a particularly important period in sleep development and toddlers are often encouraged to take a daytime nap, although by the age of two a child will usually be getting most of their sleep during the night.
Researchers in Australia analysed other relevant studies around the world including one which found that among children attending a nursery school where napping was optional, the onset of sleep was later on evenings following a nap compared with days where they had not taken one.
Napping was also not found to be a response to shorter sleep duration the night before.
Other studies included one which found that longer naps among children aged from four to six were associated with greater anxiety and/or depression and withdrawal, while another made a link between the same symptoms and difficulty in settling for naps in children aged one to three.
But the report, published in Archives of Disease in Childhood, found the relationship between napping and its effects on other aspects of children's development to be less clear.
The work was led by Professor Karen Thorpe, of the School of Psychology and Counselling at Queensland University, who said further research involving more systematic studies should be carried out.
"The duration and quality of sleep have immediate, ongoing and long-term consequences for child development and health," she said.
"During early childhood, sleep patterns affect the individual child and can also have a profound effect on family functioning and parent well-being.
"The impact of night sleep on children's development and health is increasingly documented, but to date there is not sufficient evidence to indicate the value of prolonging napping, whether at home or in childcare contexts, once sleep has consolidated into night."