Neuropeptide Y system in mood disorders: role of the different receptor subtypes

Depression has been described by mankind for several millennia. The term melancholia, which means “black bile” in Greek, was first used by Hippocrates around 400 b.C. (Akiskal et al., 2000). The major symptoms of depression and the comorbidity of depression with anxiety and excessive alcohol consumption were recognized in ancient times, indeed similarities between ancient descriptions of depression and those of the modern era are striking. From the middle part of the 19th century the brain became the focus of the efforts to understand the pathophysiology of depression. Today, depressive disorders represent a common psychiatric disorder experienced by more than 10% of the population at least once during the lifetime (Blazer et al., 1994). Women are more prone to the disease than men, with almost a two-fold lifetime prevalence rate: around 21% of women and 13% of men of the Unites States population. The mortality is high: 70% of all suicides can be attributed to depressive disorders and they represent a major cause of morbidity worldwide: studies in the United States suggest that 2–3% of the population is hospitalized or seriously impaired by affective illnesses (Blazer, 2000). The World Health Organization has declared depression as the single largest cause of morbidity for women and the leading cause of disability worldwide. Despite the devastating impact of depressive disorders, little is known about their etiology and pathophysiology.