Depression is characterized by a state of low mood and loss of interest in activities that can affect a person’s thoughts, behavior, feelings and sense of well-being. Depressed people experience anxiety, hopelessness, worries, helplessness, worthlessness, guilt, hurt and restlessness. They may also experience loss of appetite or overeating, have problems concentrating, remembering details, or making decisions, and may contemplate or attempt suicide. Insomnia, excessive sleeping, fatigue, loss of energy, or aches, pains, or digestive problems that are resistant to treatment may also be present. 
People experience some form of depressive episodes at some point but when such symptoms interferes significantly with everyday functioning, it becomes a problem to be addressed my a medical or psychiatric practitioner. Major depressive episodes, bipolar disorder and some other psychiatric illnesses have depression as a symptom.
Depression is caused by a combination of genetic, biological, environmental, and psychological factors. Depressive illnesses are disorders of the brain. Brain-imaging technologies, such as magnetic resonance imaging (MRI), have shown that the brains of people who have depression look different than those of people without depression. The parts of the brain involved in mood, thinking, sleep, appetite, and behavior appear different. But these images do not reveal why the depression has occurred. The diagram below shows the difference in brain wave patterns of normal and depressive brain using the electroencephalogram (EEG)
Some types of depression tend to run in families. However, depression can occur in people without family histories of depression too. Scientists are studying certain genes that may make some people more prone to depression. Some genetics research indicates that risk for depression results from the influence of several genes acting together with environmental or other factors. In addition, trauma, loss of a loved one, a difficult relationship, or any stressful situation may trigger a depressive episode. Other depressive episodes may occur with or without an obvious trigger.
If you identify with several of the following signs and symptoms, and they just won’t go away, you may be suffering from clinical depression.
- you can’t sleep or you sleep too much
- you can’t concentrate or find that previously easy tasks are now difficult
- you feel hopeless and helpless
- you can’t control your negative thoughts, no matter how much you try
- you have lost your appetite or you can’t stop eating
- you are much more irritable, short-tempered, or aggressive than usual
- you’re consuming more alcohol than normal or engaging in other reckless behavior
- you have thoughts that life is not worth living (seek help immediately if this is the case)
excerpt from www.helpguide.org
Before resorting to the psychiatrist, psychologists can help proffer solutions that are non-invasive and long lasting.
Neurofeeedback, Biofeedback and Audio-Visual Entrainment are tools which can be used to combat depressive symptoms.
