Depression is a serious medical problem that concerns the brain. Patient with depression have a feeling of being sad, blue, unhappy, miserable or down in the dumps. Many of us feel this way at some point of time for shorter durations. True clinical depression is a mood disorder where the feelings of sadness, anger or frustration tends to interfere with the day to day activity for a longer duration.

Depression seen in adolescence is termed as adolescence depression. Adolescence depression is a disorder which is found in the teenage time. It usually involves lack of interest in day to day activities, lack of self esteem, feeling sad and lonely. When a person shows five or more symptoms of depression in a period of 2 weeks then it is termed as major depression. The symptoms are feeling sad, hopeless, worthless or pessimistic. A difference in behavior is also found in people like prominent change in sleeping and eating scenario that can adversely affect a person's family, social life and general health.

The following diseases come under the depression spectrum:

1. Major depressive disorder: Major depressive disorder is characterized by low mood, low self-esteem and loss of interest in normally enjoyable activities.

2. Dysthymia: Dysthymia is characterized by chronic depression. Patient experience atleast 2 of the following symptoms like feelings of hopelessness, hyper or insomnia, fatigue, lack of self esteem, lack of concentration and poor appetite or overeating.

3. Bipolar disorder: Bipolar disorder is also referred as manic depressive disorder or bipolar affective disorder. It is a psychiatric condition that is characterized by the presence of one or more episodes of abnormally elevated mood clinically or mania or in some case it is milder it is called as hypomania.

4. Cyclothymia: This disorder is a milder form of bipolar II disorder which is characterized by recurrent mood disturbances between hypomania and dysthymic mood.

5. Bulimia Nervosa: Bulimia nervosa is an eating disorder which is characterized by recurrent binge eating i.e. episodes of uncontrollable overeating that is followed by compensatory behaviors. It is found that about 70% to 85% of the patient suffering from depression develops bulimia nervosa.

6. Anorexia Nervosa: Anorexia nervosa is a psychiatric condition characterized by extremely low body weight with the fear of gaining weight.

7. Schizoaffective disorder: Schizoaffective disorder is a psychiatric condition which is characterized by recurring episodes of mood disorder and psychosis. Distortions in perception occur along with elevated or depressed mood. These perceptual disortions can affect all five senses.

8. Seasonal affective disorder (SAD): Seasonal Affective Disorder (SAD), also known as winter depression or winter blues. People suffering with this are normal except for in winter season.

9. Adjustment disorder with depressed mood: Adjustment disorder (AD) is a mental disorder that is that is characterized by significant emotional or behavioral symptoms that are not related to any other specific disorders.

10. Postnatal depression: Postpartum depression (PPD) affects women and less frequently men after childbirth. It is found to be common in pregnant women.