Symptoms of depression help the patient make a diagnosis. The absence of such symptoms should alert the specialist to unipolar personality disorder, including masked depression. A distinctive feature of depressive disorder is a combination of several signs and symptoms, each of which is individually present in the main and secondary types of the disorder. In the case of a unipolar form of depression, the signs of the disease may have some features. One or more of the underlying symptoms of depression occur consistently in the patient, indicating a severe form of the disorder. The presence of several fundamental signs allows the disorder to be classified as a more severe form of depression. Episodes of severe symptoms indicate the monotypic nature of unipolar disorder.