Neurosis is a functional (reversed) mental disorder, caused by the influence of psychotraumatic factors for fully keeping of awareness of the diseases and adequate reflection of the real world.
The term "neurosis" and its first definition were given by W. Cullen (1769, 1777), who described all mental disorders under this name including those that are nowadays related to neuroses (hysteria, fears, hypochondria and mild cases of melancholy).
V.A. Gilyarovsky identified several basic indicators of neuroses: psychogenic, psychologically understandable mechanism of disorders, personality characteristics, vegetosomatic disorders, desire to overcome the disease, person's comprehension of the pathogenic situation and painful symptoms. The mechanism of struggle and defence varies for different types of personality and different neuroses. For a generally favourable course of the disease, its duration can vary. In some cases, full recovery does not begin and pathological types of behaviour of patients, who get used to the disease, become casual for a long time. This state is called neurotic personality development.
There is no uniform classification of neuroses. In ICD-10 classification is based on indication of the key symptom: phobias (F40), fear and panic attacks (F41), obsessions (F42), melancholia, depression (F42.2), conversional mental and neurological disorders (F44), hypochondria and dysmorphobia (F45.2), somatovegetative dysfunction (F45.3), pains (F45.4), asthenia (F48.0), depersonalisation (F48.1).
Three main types of neurosis are distinguished in Russian psychiatry: neurasthenia, hysterical neurosis, obsessive-compulsive neurosis. Nowadays, the diagnoses "hypochondriacal neurosis" and "depressive neurosis" are not made since the phenomena of summarisation and affective disorder can be present in any neurosis. For the same reasons, the terms "gastric neurosis", "cardiac neurosis", etc., are not used.