Holiday depression is a type of an affective disorder that occurs during the holidays and can affect anyone. It is still not classified as an official diagnosis, but it shares similarities with the diagnoses of depresive episode, seasonal affective disorder and anniversary reaction. Holiday depression is a phenomenon that most people experience in their lives, and it is characterized mostly by low mood and anxiety. It most often appears as a reaction to an unresolved trauma from the past combined with a feeling of pressure created by the environment that it is a period in which everything should be idyllic, which further aggravates the symptoms. The symptoms of holiday depression are not particulary worrisome and subside with the passing of the holidays, however, for any person who goes through them, they are an extremely unpleasant experience. Seasonal affective disorder is a subtype of depression characterized by the onset of depressive symptoms in autumn or winter with spontaneous remission in spring or summer for at least two years in a row. It affects women 2-4 times more often than men and its overall prevalence is 5-10% and increases linearly with increasing degrees of latitude. Seasonal affective disorder is caused by changes in a persons circadian rhythm, changed sensitivity of the retina of the eye to the light during the winter period, and also has a genetic basis. It is presented with different symptoms depending on age, so younger people experience more symptoms than the adults, which usually experience hypersomnia and hyperphagia only. It can be successfully treated with psychopharmaceutic drugs, psychotherapy and bright light therapy.