Do you have to have a reason to feel depressed?

Not really sometimes it is caused by emotionally being drained from working too hard or just sitting and doing nothing

Not necessarily. There can be a variety of reasons that we can feel depressed. Sometimes it could be hormone imbalances, something that happens a lot when we're teenagers. Sometimes its a reaction to something significant that has happened in our lives, and sometimes, there isn't necessarily a particular reason that we feel the way we do. The important thing to do when you sense that you aren't yourself, is to get help as soon as you can. It only makes it so much harder when we try to battle depression by ourselves, even if we don't want anyone to know, or the extra company. As people, we were made to be in community with each other, to support one another.

No - there doesn't have to be a reason. Depression can affect us all and there isn't always a clear reason why. Fortunately there is a lot that can be done to overcome depression! Start by talking to someone about it, getting regular exercise and having some productive hobbies such as art or an instrument. Try to accept positivity into your life.

No, you do not. While Depression can be a symptom of physical illnesses (thyroid problems, Vitamin D deficiency etc.) or be a reaction to an event or a drug, it can be "idiopathic" as doctors would say, which means without obvious cause. And even if there was a cause there is no need to know the cause for the feelings to be valid.

No, you don't need a reason for any emotion or feeling, but if this is something that is ongoing, there may be a bigger issue at hand.

No you do not. Depression is a mental illness. Just like there is no reason someone might get cancer there is no reason why someone might get depression. Be kind on yourself and always use resources to broaden your knowledge.

Many people don't, or they can't pinpoint a specific reason. Sometimes depression may be caused by the accumulation of small failures, or a big failure, or big grief, anything.

Plenty. Past bullying at school, being abused in a relationship, grief from losing my dad and daughter, low self esteem by my appearance, break ups.

Not always, however there must be a trigger to it. Sometimes we forget to attend to our little problems that we don't realise it grows into something deeper. No matter what causes it, what you feel is what you feel even though sometimes it is hard to translate this into reason.

Depression is a very multifaceted experience, which can make it very difficult to pinpoint its underlying reason(s). That's why so many have found joining forces with a professional (counselor, psychiatrist, etc.) extremely valuable when tackling depression: they are able to use their own self-knowledge and the skills of the professional to track down the reason(s) for the depression and the best way(s) to begin resolving it. tl;dr - I believe so, but that doesn't mean finding it is always easy.