There is no simple explanation. If there was than many people would be able to improve. Clara22 provided an extensive list and one I find the most intelligent. It is not solely brain dysfunction. Antidepressants are not doing a good enough job. People don't want to be hooked on antidepressants for life. Especially when they become ineffective. Since the World Health Organization is reporting a global increase in depression we must orient globally. What is happening? Global pollution, overpopulation, inequality with regards to resources, violence, lack of community etc. I really think in order to cure depression and anxiety one has to sit down and list all the possible causes and then one by one come up with ways to alleviate the cause in order to produce a different effect. Can you see the amount of work this takes? One would have to come up with a checklist and make sure they are doing positive things everyday. If anxiety and agoraphobia are the problem then the person must use exposure therapy. Radical solutions may be needed as moving from one state to another, or even one country to another. One really needs to attack the problem with no let up. I think maybe there are about 200 causes for my depression. I think I may sit down and write up a list and possible solutions. It is a complex problem and requires a deep and vigorous palette of solutions.