Daily doses of darkness (and light) differentially determine the development of depression

It has previously been reported that inhabitants of northern latitudes  are more susceptible to clinical depression and substance abuse during the winter solstice. In addition to these major psychiatric disorders, these individuals are also at risk for developing SAD (seasonal affective disorder), a milder form of depression. Obviously, predispositions to these psychiatric disorders manifest from chronic exposure to constant darkness. Preventative and nonpharmacological treatments include bright light therapy and exercise.

Of dual interest, a recent report claims that too much light exposure and subsequent insomnia during the summer solstice increases suicidal attempts .  I imagine that insomnia associated with exposure to constant light also increases risk taking behavior, and impairs cognition and performance, as previously reported.

As a side note, our lab has found that constant light exposure potentiates ethanol preference and ethanol consumption in mice, indicating these individuals may also be at risk for developing substance abuse. Neurochemically, the increased suicidal attempts may be attributed to depressed serotonin levels associated with constant light exposure; another discovery from our lab. As a reminder, a retardation in serotonin release at the synapse, or a high rate of serotonin reuptake from the synapse are dually responsible for the development of depression, anxiety, and subsequently, suicidal behavior. I’m sorry, Sarah Palin, but Alaska isn’t as alluring as you say.


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