Not all large epidemiologic investigations, however, have identified persistent sleep disturbance as a risk factor for incident depression. The Nord-Trondelag Health Study (HUNT)-1 and HUNT-2 are countywide Norwegian health surveys conducted about a decade apart in > 85,000 adults. Neckelmann and colleagues12 analyzed a sample of participants who had no evidence of significant anxiety or mood disorder at the time of initial (HUNT-1) assessment to determine the relationship between the presence of insomnia at either assessment point (ie, at HUNT-1 or HUNT-2), or at both, with development of new-onset anxiety or depression as determined at HUNT-2 assessment. Their results appear to confirm previous data that suggest chronic insomnia is a risk factor for anxiety disorder. Onset of anxiety disorders was significantly greater in participants who had insomnia at HUNT-1 alone, HUNT-2 alone, or at both points. In contrast to results from numerous other epidemiologic surveys, however, development of major depression (as determined at HUNT-2) was associated only with presence of insomnia at HUNT-2. As stated by the authors, these results suggest that, although chronic insomnia appears to represent a trait marker for increased risk of developing an anxiety disorder, the relationship between insomnia and depression, in this study at least, is state dependent. The length of the follow-up (11 years) in this study reduces the chances that insomnia cases identified at the first assessment represented a prodromal symptom of a depression that was identified at the second assessment. The authors also noted that correcting for comorbidity between anxiety and depression reduces the potential confound that associations between insomnia and depression are, in fact, a function of comorbid anxiety.