A study into teenage sleeping patterns has found depression and anxiety are leading causes of sleep disorders.
Researchers at Auckland University and Manukau District Health Board used a questionnaire to obtain information from 1388 high school students.
The results show 37.2% of teenagers had a sleep disorder lasting more than a month.
University Medical School senior lecturer Tony Fernando said the main reasons for the disorders include depression, anxiety and alcohol use.
At one of the six schools surveyed, the rates of sleep disorders were particularly high, at 56.8%.