Clinical depression 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 "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. It often leads to constant negative thinking and sometimes substance abuse.
Some of the symptoms  of depression include:
- Heightened irritability and restlessness
- Changes in weight and appetite
- Feelings of pessimism, sadness, hopelessness
- Empty "mood"
- Changes in sleeping pattern - early awakening or insomnia or oversleeping
- Loss of interest in activities and hobbies which were enjoyable earlier
- Loss of interest in sex
- General decrease in energy and general slow down
- Feelings of fatigue without any real cause
- Feelings of guilt, remorse, helplessness, worthlessness, etc.
- Lack of concentration; difficulties in recalling and remembering
- Difficulty in making choices and decisions
- Thoughts of suicide and death
Depression and diabetesEdit
A 2007 study published in Archives of Internal Medicine found that depression can trigger type 2 diabetes in older adults.  The 10-year study followed over 4,000 subjects, and found an association between increasing feelings of depression and the incidence of diabetes -- even after factoring out lifestyle issues such as obesity and lack of physical exercise.
Mercedes Carnethon, lead author of the study and assistant professor of preventive medicine at Northwestern's Feinberg School of Medicine, suggests that the link may be a high level of cortisol, a stress hormone that may decrease insulin sensitivity: "When you're depressed or under stress your body is trying to keep glucose in the bloodstream because it needs it for immediate energy. So, it's blocking insulin action. And you may even be producing more glucose because your body thinks it needs the sugar." 
The study highlights the importance of paying attention to the signs of depression, including loss of interest in daily activities, impaired thinking and concentration, sleep disturbances and feelings of worthlessness.
Depression is a treatable disorder. Even if a person has other illness or physical complications (including diabetes), depression can be treated. Treatment of depression of a person with diabetes should, however, be managed by trained health care personnel like a psychiatrist, a psychologist, or a clinical social worker, and the health care personnel should work in close liaison with the physician rendering treatment for diabetes. This is necessary to avoid combination of potentially harmful drugs which may not be compatible if administered at the same time. There may be cases when a person first develop diabetes than depression may develop or the vice versa. In any case, the person concerned should disclose the full and complete range of medicines being taken by them to his / her physician treating diabetes, as also to the health care person providing assistance in the treatment of depression.
- ↑ Carnethon, Mercedes; M. Biggs, J. Barzilay, N. Smith, V. Vaccarino, A. Bertoni, A. Arnold, D. Siscovick (April 23 2007). "Longitudinal Association Between Depressive Symptoms and Incident Type 2 Diabetes Mellitus in Older Adults". Archives of Internal Medicine 167 (8): 802-807.
- ↑ "Depression May Trigger Diabetes In Older Adults", Medical News Today, April 24, 2007.
- ↑ Diabetes Monitor