For depression, there are many causes. Nerve cells in the brain use chemicals to communicate with each other and an imbalance in some of these chemicals can lead to depression. If a family member or relative had depression before, it also increases the risk. It is also believed that negative ways of thinking as well as difficult past experiences can all contribute to depression. Social issues such as losses, poor support network, economic difficulties and excessive stress are important considerations in depression. It is the interplay of all these factors that eventually lead to depression rather than one single cause.