Social Psychiatry and Psychiatric Epidemiology

, Volume 41, Issue 8, pp 611–618

Increase in schizophrenia incidence rates: findings in a Canadian cohort born 1975–1985

  • Isabelle Bray
  • Paul Waraich
  • Wayne Jones
  • Serena Slater
  • Elliot M. Goldner
  • Julian Somers



Results from previous studies on the incidence rates for schizophrenia are inconsistent, with some showing a declining rate [e.g., Suvisaari et al. (1999) Arch Gen Psychiatry 56:733–740] and others showing an increasing rate [e.g., Boydell et al. (2003) Br J Psychiatry 182:45–49].


This study examines (1) whether incidence rates are changing, (2) relationships amongst changing incidence rates and age, period and cohort effects, and (3) the impact of rate changes on rate projections.


A care-based cohort study carried out in British Columbia, Canada, 1989–1998. Bayesian statistical analyses were used to estimate rates and describe secular effects. Classical tests of significance were used to assess the relative importance of age, period and cohort effects.


Between 1989 and 1998, median rates per 100,000 persons changed from 77.1 (90% credible interval (CI): 42.1–137.7) to 89.9 (90% CI: 80.1–100.1) in females, and from 66.6 (90% CI: 38.8–113.3) to 119.6 (90% CI: 107.4–132.4) in males. Age effects were active for both males and females. Period and cohort effects were stronger for males than females.


In contrast to most previous studies, we found an increasing incidence of schizophrenia. Precise projections of schizophrenia incidence beyond 5 years require large sample sizes over prolonged periods of follow-up.

Key words

schizophrenia incidence epidemiology cohort study administrative data Bayesian statistics  


  1. 1.
    Geddes J (1993) Persistence of decline in diagnosis of schizophrenia among first admission to Scottish hospitals. Br J Psychiatry 163:620–626PubMedGoogle Scholar
  2. 2.
    Osby U, Hammar N, Brandt L, et al. (2001) Time trends in first admissions for schizophrenia and paranoid psychosis in Stockholm County, Sweden. Schizophr Res 47:247–254PubMedCrossRefGoogle Scholar
  3. 3.
    Suvisaari JM, Haukka JK, Tanskanen AJ, et al. (1999) Decline in the incidence of schizophrenia in Finnish cohorts born from 1954–1965. Arch Gen Psychiatry 56:733–740PubMedCrossRefGoogle Scholar
  4. 4.
    Takei N, Lewis G, Sham PC, Murray RM (1996) Age-period-cohort analysis of the incidence of schizophrenia in Scotland. Psychol Med 26:963–973PubMedGoogle Scholar
  5. 5.
    Bromet EJ, Fenning S (1999) Epidemiology and natural history of schizophrenia. Biol Psychiatry 46:871–881PubMedCrossRefGoogle Scholar
  6. 6.
    Oldehinkel AJ, Giel R (1995) Time trends in the care-based incidence of schizophrenia. Br J Psychiatry 167:777–782PubMedCrossRefGoogle Scholar
  7. 7.
    Kendell RE, Malcolm DE, Adams W (1993) The problem of detecting changes in the incidence of schizophrenia. Br J Psychiatry 162:212–218PubMedGoogle Scholar
  8. 8.
    B.C. Statistics (2002) Population Section, Ministry of Finance and Corporate RelationsGoogle Scholar
  9. 9.
    Larsen TK, Friis S, Haahr U, et al. (2001) Early detection and intervention in first-episode schizophrenia: a critical review. Acta Psychiatr Scand 103:323–334PubMedCrossRefGoogle Scholar
  10. 10.
    Jablensky A, Sartorius N, Ernberg G, et al. (1992) Schizophrenia: manifestations, incidence and course in different cultures. A World Health Organization ten-country study. Psychol Med Monogr Suppl 20:1–97PubMedCrossRefGoogle Scholar
  11. 11.
    Iacono WG, Beiser M (1992) Are males more likely than females to develop schizophrenia? Am J Psychiatry 149:1070–1074PubMedGoogle Scholar
  12. 12.
    Boyd M, Vickers M (2000) 100 years of immigration in Canada. Can Soc Trends 58Google Scholar
  13. 13.
    Clayton D, Schifflers E (1987) Models for temporal variation in cancer rates II: age-period-cohort models. Stat Med 6:469–481PubMedGoogle Scholar
  14. 14.
    Berzuini C, Clayton D (1994) Bayesian analysis of survival on multiple time scales. Stat Med 13:823–838PubMedGoogle Scholar
  15. 15.
    Osmond C, Gardner MJ (1982) Age, period and cohort models applied to cancer mortality rates. Stat Med 1:245–259PubMedGoogle Scholar
  16. 16.
    Holford TR (1991) Understanding the effects of age, period and cohort on incidence and mortality rates. Ann Rev Public Health 12:425–457CrossRefGoogle Scholar
  17. 17.
    Bashir S, Estève J (2001) Projecting cancer incidence and mortality using Bayesian age-period-cohort models. J Epidemiol Biostat 6:287–296PubMedCrossRefGoogle Scholar
  18. 18.
    Bray I (2002) Application of Markov chain Monte Carlo methods to projecting cancer incidence and mortality. J R Stat Soc Ser C Appl Stat 51:151–163CrossRefGoogle Scholar
  19. 19.
    Knorr Held L, Rainer E (2001) Prognosis of lung cancer mortality in West Germany: a case study in Bayesian prediction. Biostatistics 2:109–129PubMedCrossRefGoogle Scholar
  20. 20.
    Tsuchiya K, Monk-Jorgensen P (2002) First admission rates of schizophrenia in Denmark, 1980–1997: have they been increasing? Schizophr Res 54:187–191PubMedCrossRefGoogle Scholar
  21. 21.
    Preti A, Miotto P (2000) Increase in first admissions for schizophrenia and other major psychoses in Italy. Psychiatry Res 15(94):139–152CrossRefGoogle Scholar
  22. 22.
    Crocetti GM, Lemkau PV, Kulcar Z, et al. (1971) Selected aspects of the epidemiology of psychoses in Croatia, Yugoslavia. 3. The cluster sample and the results of the pilot survey. Am J Epidemiol 2:126–134Google Scholar
  23. 23.
    Dohrenwend BP (1980) Mental illness in the United States: epidemiological estimates. Praeger Publishers, New YorkGoogle Scholar
  24. 24.
    Harvey CA, Pantelis C, Taylor J, et al. (1996) The Camden Schizophrenia Surveys. II. High prevalence of schizophrenia in an inner London borough and its relationship to socio-demographic factors. Br J Psychiatry 168:418–426PubMedCrossRefGoogle Scholar
  25. 25.
    McCreadie RG, Leese M, Tilak Singh D, et al. (1997) Nithsdale, Nunhead and Norwood: similarities and differences in prevalence of schizophrenia and utilization of services in rural and urban areas. Br J Psychiatry 170:31–36PubMedGoogle Scholar
  26. 26.
    Boydell J, Van Os J, Lambri M, Castle D, Allardyce J, McReadie R, Murrary M (2003) Incidence of Schizophrenia in south-east London between 1965 and 1997. Br J Psychiatry 182:45–49 PubMedCrossRefGoogle Scholar

Copyright information

© Steinkopff Verlag Darmstadt 2006

Authors and Affiliations

  • Isabelle Bray
    • 1
  • Paul Waraich
    • 2
  • Wayne Jones
    • 3
  • Serena Slater
    • 2
  • Elliot M. Goldner
    • 3
  • Julian Somers
    • 2
    • 3
  1. 1.Dept. of Social MedicineUniversity of BristolBristolUK
  2. 2.Mental Health Evaluation & Community Consultation Unit (MHECCU)University of British Columbia VancouverCanada
  3. 3.Faculty of Health SciencesSimon Fraser UniversityVancouverCanada

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