Intense nihilism, somatization and agitation in old age are the hallmark symptoms of

Involutional Melancholia Described by Kraepelin, this is a form of severe depression which occurs in the involutional period of life (i.e. 40-65 years of age). It is typically characterised by marked agitation, the presence of psychotic features (such as delusions of persecution, tactile and auditory hallucinations) and multiple somatic symptoms (or hypochondriacal delusions). Ref: A Sho Textbook of Psychiatry, Niraj Ahuja, 7th Edition, pg. no.80