HTR1A and sleep disorder: For example, antagonism of 5-HT2C and 5-HT7 results in significantly increased therapeutic effects of SSRIs22, 23, 24, 25 and SSRI/5-HT1A antagonist co-administration leads to increased extracellular 5-HT levels and enhanced antidepressant responses.26, 27 However, these and other 5-HT receptors are also implicated in the side effects of SSRIs, like sexual dysfunction (5-HT1A),28 sleep disturbances (5-HT7,29 5-HT1A30), nausea (5-HT3B31) and decreased appetite (5-HT2C,32 5-HT1B33).