Depression

Clinical depression (also called major depressive disorder, or sometimes unipolar when compared with bipolar disorder) is a state of intense sadness, melancholia or despair that has advanced to the point of being disruptive to an individual's social functioning and/or activities of daily living. Although a low mood or state of dejection that does not affect functioning is often colloquially referred to as depression, clinical depression is a clinical diagnosis and may be different from the everyday meaning of "being depressed". Many people identify the feeling of being depressed as "being blue", "feeling sad for no reason", or "having no motivation to do anything". One suffering from depression may feel tired, sad, irritable, lazy, unmotivated, and apathetic. Clinical depression is generally acknowledged to be more serious than normal depressed feelings.
The relationship between depression and neurological disease is complex. Whilst many patients report transient episodes of depression, the prevalence of diagnosed clinical depression is thought to be relatively low. Diagnosis is made more complicated by the fact that several diagnostic markers of depression, such as insomnia, fatigue, and loss of appetite can be symptoms of the primary disease rather than depression. However they could also be symptoms of depression which are falsely attributed to the primary condition.
Evidence from neurology (and general practice) suggests that doctors may not give sufficient attention to patients' mental state, preferring to focus on physical disability. Therefore it is important that patients routinely mention their mental state during doctor visits and ask for help where it is needed.