Symptoms of depression: Symptoms and warning signs of depression can vary depending upon the patient’s age, for example children often show physical symptoms (such as stomachaches or headaches) and are irritable, whereas adolescents experience a sad mood, sleep disturbances and decreased energy levels.  Depression is often misdiagnosed in elderly people as this group generally experience physical problems rather than emotional problems.  The causes of depression are often unknown.  For some people, depression is triggered by an event or loss, for other people there is no apparent reason.  Likewise, depression symptoms may vary significantly between people. Common symptoms of depression include persistently feeling sad, loss of enjoyment in activities, changes to sleeping or eating habits, or a feeling of worthlessness, these symptoms are often recurrent.