Depression can be easy to overlook, as many people think it means you must feel blue all the time. But that isn't always the case. A depressed person can have ups and downs just like anyone, but that does make it harder to detect.

A depressed person often isolates themselves. Someone who doesn't get out of the house much or takes measures to avoid going in public could be depressed. They might also have social anxiety, but if that behavior couples with some others it could be a sign of depression.

Lack of motivation is often another indicator of depression. If tasks never get done around the house or at work and there is always an excuse for that, the person may be depressed. Because depression affects the brain it affects how a person functions in life all-around.

Fatigue is a big sign as well. The depressed person cannot seem to get enough sleep and sometimes has trouble falling asleep at night. Sleep troubles, whether sleeping too much or insomnia, may be the first indicator there is trouble with someone and they need to seek professional help.

Eating habits can also be affected. A person could go either way, eating too much or too little. An extreme in each direction indicates an imbalance in life somewhere and depression is a disease to consider.

Someone who drinks alcohol, abuses drugs or is obsessive-compulsive in some way often has trouble with depression. Since depression can be an out-of-control feeling, a person will seek any comfort they can to soothe what ails them. Many forms of addiction arise from depression itself.

Troubles in personal relationships can stem from depression. Since the mental illness affects a person's own life and level of functioning it is bound to affect others in the family as well, far or near from the sick person.

Thoughts of suicide often plague depressed individuals. Since life seems worth not having anymore because the mental illness has encompassed so much of life, death often seems the answer.

Lethargic behavior often occurs with depression. Someone who sits in front of the television for hours on end or won't leave the bedroom all day is probably depressed for one reason or another.

The previous factors needn't all be present for someone to be depressed. Depression itself can arise from hormonal imbalances or difficult situations in life. But no matter what the cause, a depressed person needs professional help to regain their life and enthusiasm to live before it is too late.