Australian researchers say children who are anxious can also suffer from night-time fears and restless sleep - the researchers from Macquarie University's Centre for Emotional Health say the problems may be more evident in school time.
A new study led by Associate Professor Jennifer Hudson, set out to examine subjective reports of sleep-related problems in children with anxiety disorders during school and weekend nights.
The study involved 37 children with clinically-diagnosed anxiety disorders and 26 children without anxiety disorders - all aged 7 to 12 years and the children kept an on-line sleep diary to track sleep patterns across school nights and weekend nights.
The researchers say coping with routine sleep problems in children can be stressful for both parents and the children and is more so when a child has an anxiety disorder.
By comparing the two groups of children the researchers were able to pinpoint a number of issues.
The researchers say the majority of childhood sleep problems such as delays going to sleep, night-time fears and difficulty sleeping alone, gradually resolve themselves as children age but for some children, anxiety about a range of issues leading to difficulty sleeping or falling asleep, may persist and can eventually cause more serious problems later in life if left untreated.
The research team found that one in five anxious children have insufficient sleep while one in three have difficulty falling asleep and that children with anxiety disorders go to bed much later and had considerably less sleep compared to non-anxious children - a significant finding was that the sleep disturbances did not occur on weekends and appeared to be limited to school nights.
During the week, the researchers found that school-aged children with anxiety disorders slept 30 minutes less than non-anxious children, but anxious children fell asleep quicker and were less awake on weekend nights.
Professor Hudson says that while 30 minutes less sleep per week night may appear small, the cumulative effect and its potential consequences on daytime performance may be significant as children's sleep is crucial for their overall quality of life and sleep problems are associated with a range of cognitive and emotional difficulties.
Experts say childhood sleep problems are associated with a range of adverse cognitive and academic outcomes, as well as increased impulsivity and emotional disorders such as anxiety and depression.
Professor Hudson says the research shows how important it is to treat sleep-related problems in anxious children and the need for them to be resolved them as quickly as possible.
The study is published in the international journal, Behaviour Research and Therapy.