Some people develop depression later in life as an adult and it doesn't relate to their childhood or brain chemistry or genetics. Its a result of major stressful traumatic experience. Some people have depression for short duration or manage to overcome it. Others have mod-severe depressive episodes which can be triggered by certain factors. If you view depression as all bad and out of your control then you dont give yourself chance to understand and tackle issues you need and make changes. Whether depression is mental or physical illness related to gentics, biology or negative stressful circumstances will always receive different views and responses from different people. Depression is not one way and same for everyone or limited to certain types of people getting it.