Lexapro is an anti-depressant and classified as a selective serotonin reputake inhibitors (SSRI). FDA approved usage for Lexapro (escitalopram) includes acute and maintenance treatment of major depressive disorder in adults and in adolescents 12 to 17 years of age. It is also indicated for the acute treatment of generalized anxiety disorder (GAD) in adults. Off label treatment (not approved by the FDA) includes social anxiety disorder, obsessive compulsive disorder, post traumatic stress disorder, panic disorder, and bipolar depression.
SSRI's such as Lexapro not only increase extracellular levels of serotonin, they also encourage the growth of new brain cells in the two hippocampus areas of the brain, to replace those damaged/killed by chronic stress hormone exposure. This is why anti-depressants take time to work. Degrees of improvement are usually seen between 3 and 12 weeks of treatment.
I hope this helps to further answer your question, LK. The very best to you!... Chuck