sentence: In humans , the suppression of nocturnal melatonin secretion by light is the standard measure of circadian photosensitivity ; there is some evidence that this response is upregulated in bipolar disorder and seasonal affective disorder [ 76 ] , but such studies have not been undertaken in individuals with schizophrenia.It is possible that the enhanced light-induced phase delays shown by Grm2 / 3 mice reflect the absence of mGlu2 and / or mGlu3 from RHT-SCN synapses .