Clinical Psychobiology, Branch, National Institute of Mental Health, Bethesda, MD 20892-1390.
1,25 (OH)2 vitamin D3 levels were assessed in nine females and six males with winter seasonal affective disorder and in 15 age- and gender-matched controls in winter during periods with and without treatment with light therapy. No difference was found between groups or across conditions, though wide variations within each group make the presence of a type II error possible.