Being depressed typically means being sad or blue for some reason, and the cause of the depression can be many things. Breaking off romantic relationship or being cheated on can cause depression, and so can the death of a pet or a beloved friend or family member. Sometimes being depressed is a mental state of mind, and there may not be an obvious cause for the negative emotions and thoughts that occur. Some depression is caused by genetics, and in other cases a sudden imbalance of chemicals in the brain is responsible.
Sometimes It's easier to pretend that you don't care, than to admit it's killing you.