The exact mechanism that allows Zoloft to combat depression, Levothyroxine 15 mcg anxiety and OCD is still not completely understood, however what researchers have noticed is that Zoloft affects the way serotonin is managed by the human body. Serotonin is part of a drug family known as selective serotonin re-uptake inhibitors (or Levothyroxine 15 mcg SSRI's). SSRI's increase the level of serotonin in the brain by inhibiting (not preventing) its breakdown. And yes, while this may seem complicated it really isn't.