Decreasing rates of incident schizophrenia cases in psychiatric service: a review of the literature

Abstract

A review of the literature shows that the admission rates of new cases of schizophrenia vary with a factor of two to five in North American studies as well as in European studies. Furthermore, the tendency has been decreasing for the last 40-50 years in Europe. Eighteen studies specifically analyzing the development over the last 20 years are reviewed. The studies preponderantly show significant decreases most probably due to the reduction of the number of available psychiatric beds alongside the decentralization of psychiatry, and to decreasing virulence of schizophrenia. Alternatively, a diagnostic delay of schizophrenia can hardly explain the decrease.

Treated incidence of first‐episode psychosis in the catchment area of EPPIC between 1997 and 2000

“…Early detection strategies might increase the treated incidence of first-episode psychosis. The relative risk of presenting with a first psychotic episode was highest in the [15][16][17][18][19] year range for females, and between 20-24 years for males. In comparison with females, males had double the rate of developing psychosis up to the age of 30 years.…”

“…year-old group (71.5%); proportions for males in the [15][16][17][18][19] year old and the 25-29-year-old groups were 64.9% and 63.1%, respectively. Table 1 details the cohort by sex and age groups.…”

“…Compared with the WHO study, incidence rates in the EPPIC catchment in [15][16][17][18][19][20][21][22][23][24][25][26][27][28][29] year olds were about three to four times higher in males and more than twice as high in females, while incidence rates in the PDS and the 1966 Northern Finland birth cohort studies lay in between.…”

“…Increased rates have been consistently observed in certain migrant groups (4)(5)(6), ethnic minorities (7,8), and in areas with high urbanicity (9)(10)(11)(12). In southeast London, the incidence of schizophrenia has doubled between 1965 and 1997 (13), where as in other sites a decline in incidence has been observed over the second half of the 20th century (14)(15)(16). Peak age of onset of schizophrenia is the second and third decade of life (2).…”

Comparing cohort incidence of schizophrenia with that of bipolar disorder and affective psychosis in individuals born in Stockholm County 1955–1967

“…The neurodevelopmental model (Murray & Lewis, 1987) proposes that exposures such as maternal stress (Huttunen & Niskanen, 1978;Khashan et al 2008;Abel et al 2014) maternal famine (Susser & Lin, 1992;Brown et al 1995;St Clair et al 2005), infections (Buka et al 2008;Sørensen et al 2009;Xiao et al 2009) and birth complications (Geddes & Lawrie, 1995;Kinney et al 1998;Kunugi et al 2001;Cannon et al 2002;Scott et al 2006;Nosarti et al 2012) during fetal/neonatal life in interaction with predisposing genes, affect the fetus to develop vulnerability for psychiatric disorders, particularly schizophrenia. Over the years, several studies have suggested that total incidence, morbid risk or first admission rate for schizophrenia has decreased during 1970-1990(Munk-Jörgensen, 1995, whereas other studies have found unchanged (Harrison et al 1991;Oldehinkel & Giel, 1995) or even increased (Tsuchiya & Munk-Jörgensen, 2002;Bray et al 2006) incidence rates during this period of time. Over the years, several studies have suggested that total incidence, morbid risk or first admission rate for schizophrenia has decreased during 1970-1990(Munk-Jörgensen, 1995, whereas other studies have found unchanged (Harrison et al 1991;Oldehinkel & Giel, 1995) or even increased (Tsuchiya & Munk-Jörgensen, 2002;Bray et al 2006) incidence rates during this period of time.…”