Antidepressant medication is usually prescribed to treat depression but is occasionally used if someone has apathy or emotional lability. It works by acting on the chemicals in the brain. Many antidepressants are very effective and about two thirds of people who take them benefit. As antidepressants take at least two weeks to work properly, it is worth persevering with them, even if you do not feel better immediately. However, as with any medication, there can be side effects, such as fatigue or a dry mouth, so you may need to try more than one type of antidepressant before you find one that is effective.