People with bipolar disorder often show variations in their moods throughout the seasons or at different times of the day. Researchers from the National Institute for Health and Welfare in Helsinki studied 122 people. 32 of them had bipolar disorder, 40 of them were first-degree - i.e. in the same nuclear family - relatives of people with bipolar disorder and 50 were unaffected controls. Among bipolar disorder sufferers and their relatives those who reported seasonal variations in mood and behaviour scored worse on tasks of manipulating shapes, visuospatial reasoning, auditory attention, working memory and verbal memory than those with no seasonal variation. Patients and relatives tested in Spring, Summer or Autumn performed better than those tested in Winter but there was no association between season and test scores among the unaffected controls.
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