It is important to emphasize that the diagnosis should be made by a psychiatrist or a psychologist, but knowing the symptoms is important in case you need to seek help. According to the health ministry the signs and symptoms are:
Besides mood changes or irritability, anxiety and anguish depression has several signs and symptoms, which can be isolated or somatized.
Depressive mood or irritability, anxiety and distress;
discouragement, easy tiredness, need for more effort to do things;
decrease or inability to feel joy and pleasure in activities previously considered pleasant;
disinterest, lack of motivation and apathy;
lack of will and indecision;
feelings of fear, insecurity, hopelessness, helplessness and emptiness;
pessimism, frequent and disproportionate ideas of guilt, low self-esteem, sense of meaninglessness in life, uselessness, ruin, failure, illness or death. One may wish to die, plan a way to die or even attempt suicide;
difficulty in concentration, slower reasoning and forgetfulness;
decrease in sexual performance (you can even maintain sexual activity, but without the usual pleasant connotation) and libido;
loss or increase of appetite and weight;
insomnia (difficulty in reconciling sleep, multiple awakenings or sensation of very superficial sleep), early morning awakening (usually two hours before the usual time) or, less frequently, an increase in sleep (you sleep too much and still get sleep most of the time);
pain and other physical symptoms not justified by medical problems, such as belly pain, poor digestion, heartburn, diarrhea, constipation, flatulence, tension in the nape of the neck and shoulders, headache or pain in the body, sensation of heavy body or pressure in the chest, among others.