Psychological Medicine



Incidence and distribution of first-episode mania by age: results from a 35-year study


N. KENNEDY a1a2c1, B. EVERITT a3, J. BOYDELL a1, J. VAN OS a1a4, P. B. JONES a5 and R. M. MURRAY a1
a1 Section of General Psychiatry, Division of Psychological Medicine, Institute of Psychiatry, De Crespigny Park, London, UK
a2 St Edmundsbury Hospital, Lucan, Republic of Ireland
a3 Department of Biostatistics and Computing, Institute of Psychiatry, De Crespigny Park, London, UK
a4 Department of Psychiatry and Neuropsychology, South Limburg Health and Teaching Network, EURON, Maastricht University, Maastricht, The Netherlands
a5 Department of Psychiatry, Addenbrooke's Hospital, Cambridge, UK

Article author query
kennedy n   [PubMed][Google Scholar] 
everitt b   [PubMed][Google Scholar] 
boydell j   [PubMed][Google Scholar] 
van os j   [PubMed][Google Scholar] 
jones pb   [PubMed][Google Scholar] 
murray rm   [PubMed][Google Scholar] 

Abstract

Background. Few epidemiological studies have investigated incidence by age or age at onset distributions for mania or bipolar disorder. The current study aimed to determine these in a defined area in south-east London, over a 35-year period.

Method. All cases of first-episode mania presenting to psychiatric services in Camberwell, south-east London, between 1965 and 1999 were identified. Incidence rates by age, using 5-year age-at-onset bands, were estimated and the structure of the age-at-onset distribution for first-episode mania was investigated using finite mixture distributions (admixture analysis).

Results. The incidence of DSM-IV bipolar I disorder (BP I), first manic episode peaked in early adult life (16·38/100000 population per year in the 21–25 years band) with a much smaller peak in mid-life. A two-component normal mixture distribution fitted age at onset better than either a single normal distribution or a three-component mixture, implying the existence of early and later onset subgroups. The early onset group had a stronger family history of bipolar disorder, and showed more acute, severe and atypical symptoms during their first manic episode.

Conclusions. The incidence of mania peaks in early adult life but there is clear evidence of early and later onset subgroups which may represent different forms of disorder.


Correspondence:
c1 Dr N. Kennedy, St Edmundsbury Hospital, Lucan, County Dublin, Republic of Ireland. (Email: nkennedy@stpatsmail.com or N.Kennedy@iop.kcl.ac.uk)


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