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. Author manuscript; available in PMC: 2019 Sep 16.
Published in final edited form as: Einstein J Biol Med. 2017;32:E13–E25.

Figure 2. Mechanisms of BLT action based on proposed pathophysiology of Seasonal Affective Disorder.

Figure 2.

(A) BLT corrects the phase delay. Pre- and post-BLT treatment are displayed as blue and purple broken lines respectively. Morning BLT treatment corrects the phase delay by shifting the circadian rhythm earlier (to the left) leading to less discordance between the circadian rhythm and the clock time/sleep-wake cycle.

(B) BLT increases available serotonin. BLT treatment during the fall/winter reduces the serotonin transporter binding potential, theoretically leading to less uptake, and a greater amount of available serotonin in the synaptic cleft.