The drug has also gained popularity in recent years as a fast-acting antidepressant medication. Unlike other antidepressants, which can take weeks or months to work, patients who take ketamine often see improvements within just a few hours. Ketamine also appears to sharply decrease thoughts of suicide. But the effects are short-lived, and the long-term outcomes of regular ketamine treatment are unknown. And research from Yale University found that ketamine improved symptoms significantly in teens who suffer treatment-resistant depression