Antidepressants can only do so much in altering substances in the brain to remove the feeling of depression. If the reason for your depression is somatic, which means it is because of imbalances in the neurotransmitters in your brain, then antidepressants can help. But if it is psychological because of several big personal issues in your life that you cannot resolve, no matter how many antidepressants you take, after the good feeling you get, you will go back to those feelings again. You cannot rely on antidepressants to make you happy again. It will really just frustrate you and you will end having more problems when you get stuck and addicted to antidepressants.
Sometimes, a cure for depression is to face up to its source which is probably something hurtful that you buried deep in your subconscious. You say that you were not this way before. What were you like before this depression set in? What happened to you that made you severely depressed?
I have known depression and how it feels when you just cannot go on with life anymore. But I also know that you have to hope and believe that everything in life has a purpose, and in time, everything will turn out right.
