At the same time, all inhabitants aged 20 or more were invited to the adult version of the survey, which consisted of a health examination and two questionnaires. The participating adolescents, of whom some were siblings, had a total of 7036 invited mothers (mean age 42.2 years, SD = 5.3), of which 71.9% replied to both questionnaires. Among 6535 invited fathers (mean age 45.2 years, SD = 5.7), 61.1% returned both questionnaires. More details regarding the HUNT-2 [42] and Young-HUNT [43] studies have been described elsewhere and are available at http://www.ntnu.edu/hunt.
