One month after her mother's death from hea failure; a 25-year-old woman with no prior psychiatric history is still very sad and tearful. She has difficulty concentrating and failing asleep at night and has lost three pounds. The most likely diagnosis is

According to the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5), bereaved individuals--or those grieving over the death of a loved one--have an extraordinarily difficult time dealing with this loss. Ref ganong's review of medical physiology 25e p641