RESUMO
Mourning is a natural response to a loss and a condition which most people experience several times during their lives. Most individuals adjust adequately to the loss of a relative, neverthless, a small but noteworthy proportion of bereaved individuals experience a syndrome of prolonged psychological distress in relation to bereavement. Prolonged distress and disability in connection with bereavement has been termed Complicated Grief (CG) or Prolonged Grief Disorder (PGD). The purpose of this paper is to analyze the literature on loss and mourning making a review of the main studies published between 1993 and 2013, identified through a search conducted on Medline/PubMed, in order to describe the epidemiological and clinical aspects of "normal" grief and "complicated" grief, pointing out the path of the clinical definition of PGD and proposed diagnostic criteria for inclusion in the next edition of the Diagnostic and Statistic Manual of Mental Disorders, Fifth edition (DSM-5). The two main diagnostic systems proposed by Horowitz and Prigerson are also compared.