title: Low doses of lithium carbonate reduce melatonin light sensitivity in healthy volunteers.
abstract: Sensitivity of the pineal hormone melatonin to bright light at night has been posited as a putative marker of affective disorders. Research demonstrates melatonin supersensitivity to light in bipolar disorder, however the role that lithium carbonate plays in this response is unclear. This study assessed the effect of lithium on nocturnal melatonin secretion and sensitivity to light in healthy adults. Ten participants, tested on two nights, had blood samples drawn between 20:00 and 02:30 hours. On testing nights participants were exposed to 200 lux of light between 24:00 and 01:00 hours. Participants took 250 mg of lithium daily for 5 d between testing nights. The results indicated that lithium had a significant effect on sensitivity to light but not on overall melatonin synthesis. This finding has implications on the true magnitude of the melatonin light response in people with bipolar disorder and may elucidate possible mechanisms of action of lithium.
authors.affiliation: Department of Psychiatry, The University of Melbourne, Austin Health, Heidelberg, Victoria, Australia. k.hallam@pgrad.unimelb.edu.au
authors.forename: Karen T
authors.initials: KT
authors.lastname: Hallam
authors.forename: James S
authors.initials: JS
authors.lastname: Olver
authors.forename: Jennifer E
authors.initials: JE
authors.lastname: Horgan
authors.forename: Caroline
authors.initials: C
authors.lastname: McGrath
authors.forename: Trevor R
authors.initials: TR
authors.lastname: Norman
mesh_terms: D000328:Adult; D018692:Antimanic Agents / Q000008:administration & dosage*; D019540:Area Under Curve; D002940:Circadian Rhythm / Q000187:drug effects*; D005260:Female; D006801:Humans; D016651:Lithium Carbonate / Q000008:administration & dosage*; D008297:Male; D008550:Melatonin / Q000009:adverse effects* / Q000378:metabolism; D010775:Photic Stimulation / Q000379:methods; D020795:Photophobia / Q000139:chemically induced / Q000188:drug therapy*
chemical_list: D018692:Antimanic Agents; D016651:Lithium Carbonate; D008550:Melatonin