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Melatonin sensitivity to dim white light in affective disorders
P J Nathan1, G D Burrows, T R Norman
1Brain Sciences Institute, Swinburne University of Technology, Victoria, Australia. pnathan@bsi.swin.edu.au
Summary
Patients with bipolar affective disorder and seasonal affective disorder show a supersensitive melatonin suppression to light. This finding differs from major depressive disorder patients, suggesting a potential biomarker for mood disorders.
Area of Science:
- Neuroscience
- Chronobiology
- Psychiatry
Background:
- Light exposure suppresses nocturnal melatonin secretion.
- Altered light response in bipolar disorder has been proposed as a trait marker, but findings are inconsistent.
- Previous studies suggest major depressive disorder patients respond similarly to controls.
Purpose of the Study:
- To investigate melatonin suppression by dim light in bipolar affective disorder (BAD), seasonal affective disorder (SAD), and major depressive disorder (MDD).
- To clarify the role of light sensitivity in the pathophysiology of mood disorders.
Main Methods:
- Melatonin suppression was measured in response to dim light (200 lux).
- Participants included patients diagnosed with BAD, SAD, and MDD, alongside controls.
Main Results:
- Bipolar affective disorder patients exhibited significantly supersensitive melatonin suppression (p < .005).
- Seasonal affective disorder patients also showed supersensitive melatonin suppression (p < .05).
- Major depressive disorder patients displayed melatonin suppression patterns similar to control groups.
Conclusions:
- Supersensitive melatonin suppression to light may be a characteristic feature of bipolar affective disorder and seasonal affective disorder.
- This hypersensitivity could be a mechanism for resynchronizing phase-delayed circadian rhythms.
- An abnormality in the retinal-suprachiasmatic nucleus pathway might underlie this altered light sensitivity in bipolar disorder.