Supersensitivity to light: possible trait marker for manic-depressive illness.

Area of Science:

• Neuroscience
• Endocrinology
• Psychiatry

Background:

• Nighttime light exposure suppresses melatonin production.
• Previous research indicated heightened melatonin suppression by light in acutely ill bipolar patients.

Purpose of the Study:

• To investigate if light-induced melatonin suppression is also increased in euthymic bipolar disorder patients.
• To explore light supersensitivity as a potential trait marker for bipolar affective disorder.

Main Methods:

• Compared melatonin level responses to light exposure in 11 unmedicated, euthymic bipolar patients and 24 matched healthy controls.
• Measured plasma melatonin levels before and after controlled nocturnal light exposure.

Main Results:

• Euthymic bipolar patients showed a twofold greater reduction in nighttime melatonin levels compared to normal subjects.
• This finding was consistent with previous observations in acutely ill patients.

Conclusions:

• Bipolar disorder patients, even when euthymic and unmedicated, demonstrate a hypersensitivity to light's melatonin-suppressing effects.
• This supersensitivity to light may represent a stable trait marker for bipolar affective disorder.