The depression is a disorder that characterises by a state of spirit depressed the main part of the day, and loss of interest by activities that before resulted pleasant.
Has to differentiate of the normal reaction of sadness that have in front of a negative event, if this sadness perdura then if it can turn into depression.
"The depression is a state of pathological sadness, accompanied of a marked decrease of the feeling of personal value and of a painful decrease of the mental activity, psicomotriz and organic"
Robert and Lamontagne,1997

Symptoms of depression:
The person can spend the main part of the day crying, be irritable, of bad humour or concern too much by his health, loses the feeling of the own value, of the own self-esteem. They find concerned and his negative thought absorbs them. It arrives a moment in that they no longer make the usual activities and despreocupan of his welfare.
In the field of the thought, has difficulty to concentrate , everything sees it black (appear the negative thoughts),feelings of uselessness and fault, can even have suicidal thoughts.

Negative thoughts as for example:

Culpability: focalizar the culpability in one same
Vision catastrofista: all see it black
Extremist thought: in the negative pole 
Interpretation of the thought: think that the other think of them negative things...

They can appear disorders of the sleep, sleeplessness or hipersomnia (dream the main part of the day).
The alimentary habits tambien change, can have an increase or considerable decrease of the appetite, with the consequent increase or decrease of the corporal weight.
All these changes produce a significant deterioration in every aspect of the life of the person ,home, the work, family, with the friends.
The depression can have an or several causes.
Causes of depression:
-Biochemical factors, can have a deficit of neurotransmisores of the brain.
-Inheritance, more probability to suffer depression if in the family has given the disorder.
-Personality, there are personalities more liable has to suffer depression.
-Diet, not having a suitable diet.
-Sleep, sleep bad or very little, on duty changes in the works.
-In the women after giving to light can appear depression.

Types of depression:
Depression Mayr: it is very incapacitante, been of sad spirit, everything sees it black, crying, tall irritability...

Cristerios For the episode depresivo main (DSM-IV-TR):

To- Presence of 5 or more than the following symptoms during at least two weeks:  one of the symptoms has to be (1) been of spirit depresivo or 2) loss of interest or of the capacity for the pleasure.

1-been of spirit depresivo the main part of the day, almost each day.
2-decrease accused of the interest or of the capacity for the pleasure in all or almost all the activities, the main part of the day or almost each day.
3-Loss of weight without doing diet or increase of weight
4-Sleeplessness or hipersomnia almost each day.
5-Agitation or enlentecimiento psicomotor almost each day.
6-fatigue or loss of energy almost each day.
7-Feelings of uselessness or of excessive or inappropriate fault (that they can be delirantes) almost each day.
8-Decrease of the capacity to think or with centring , or indecision, almost each day.
9-recurrent Thoughts of death (no only fear to the death)

B. The symptoms do not fulfil the criteria for or  mixed episode

C.The symptoms produce social deterioration, labour.. Or of other areas imporatntes of the person.

D.The symptoms are not been due to the direct physiological effects of a substance or a medical illness

And.The symptoms do not explain better by the presence of a duel, the symptoms persist during more than two months or characterise by an accused functional inability, worries of uselessness, suicidal ideation, symptoms psicóticos or enlentecimiento psicomotor.

Bipolar disorder: one or but manic episodes (state of ebullient spirit,decrease of hours of sleep, speak a lot, implication in pleasant activities that they can have grave results, like reckless driving) followed of episodes of main depression.
Distimia: The person presents been of spirit depressed during a period of time very long (more than two years),although it do not look it is very incapacitante, is not so severe like the main depression, but has to include any of the characteristics of the depression distinguishes of the main depression in base to the gravity, the cronicidad and the persistence.

The treatment cognitive therapy conductual for the depression consists in:

-Identify and racionalizar the negative thoughts that has the person.
-Learn to see the situations of realistic and objective form
-Coaching asertivo
-Coaching in taking of decisions and resolution of problems

Together with the depression also works the anxiety since depression and anxiety go related and self-esteem. - Diseño de paginas - Guia comercial de el prat