NEW YORK - For some people, chronic insomnia may be a sign of broader mental health problems like depression and anxiety, according to a new study.

In surveys of more than 25,000 Norwegian adults, researchers found that those with chronic insomnia were more likely to also be suffering from depression or an anxiety disorder.

What's more, people who reported insomnia during the first wave of the survey were at increased risk of having an anxiety disorder during the second wave, conducted a decade later.

This, the researchers say, suggests that insomnia may either raise the risk of future anxiety problems, or be a sign that a person is particularly vulnerable to developing anxiety symptoms.

The findings are published in the medical journal Sleep.

Sleep problems are common in people with depression, anxiety and certain other mental health conditions. But whether insomnia can lead to depression or anxiety is unclear.

To study the question, researchers led by Dr. Dag Neckelmann of Haukeland University Hospital in Bergen, Norway, used data from a general health survey that followed 25,130 adults age 20 and older.

Respondents were first surveyed between 1984 and 1986, then again between 1995 and 1997. Anxiety and depression symptoms were gauged during the second survey, with standard questions used to diagnose the disorders.

In general, the researchers found, people with chronic insomnia during the first survey were more likely to have anxiety disorder symptoms during the second survey - as were respondents who had insomnia during the second survey only.

This suggests that, in some people, insomnia could signal a current anxiety disorder, or be a risk factor for developing anxiety down the road, according to Neckelmann's team.

In contrast, there was no evidence that insomnia was a risk factor for future depression. Instead, people with insomnia during the second survey were at heightened risk of current depression - indicating that insomnia and depression commonly co-exist.

The findings, Neckelmann told Reuters Health, point to the importance of seeking help for chronic insomnia, as well as being evaluated for any symptoms of depression or an anxiety disorder.

Each of these disorders, the researcher noted, can be treated with non-drug options, like cognitive behavioral therapy.

However, Neckelmann said, while this study suggests that insomnia may be a risk factor for anxiety, it's not yet clear whether treating insomnia lowers the odds of future anxiety disorders.