title: Further Evidence of a Cohort Effect in Bipolar Disorder: More Early Onsets and Family History of Psychiatric Illness in More Recent Epochs.
abstract: Given that a cohort effect is rarely mentioned as one of the possible contributors to the increased incidence of childhood-onset bipolar disorder in the United States, we reexamined evidence for the phenomenon within our outpatient Bipolar Collaborative Network.
  
  
  
  968 outpatients (mean age, 41 years) with DSM bipolar disorder from 1995 to 2002 from 4 sites in the United States and 3 in the Netherlands and Germany (abbreviated as Europe) gave informed consent and provided detailed demographic, illness, and family history information on a patient questionnaire. Family history of bipolar disorder, depression, suicide attempt, alcohol abuse, substance abuse, and "other" illness was collected for each parent and the 4 grandparents. Age at onset and family history of illness burden were then assessed as a function of the age of the patient at network entry.
  
  
  
  Data for patients aged 35 years or older (n = 613) were included in the first analysis. Compared to older patients, those who were younger when they entered the network had an earlier age at onset of their bipolar disorder (r = 0.33, P < .001). Similarly, the youngest patients at entry (representing the most recent cohorts) had parents and grandparents with more psychiatric illness than patients born in earlier cohorts (n = 968).
  
  
  
  These preliminary data, taken with the substantial literature, suggest a cohort effect for earlier age at onset of bipolar disorder and greater burden of psychiatric disorders in 2 generations of direct progenitors of our patients. The resulting likely increase in severity of bipolar illness in future generations based on this earlier age at onset and increased familial loading, particularly in the United States, deserves focused clinical and public health attention and attempts at amelioration.
authors.affiliation: 5415 W Cedar Ln, Ste 201-B, Bethesda, MD 20814. robert.post@speakeasy.net.|Bipolar Collaborative Network, Bethesda, Maryland, USA.|Department of Psychiatry and Behavioral Sciences, George Washington University, Washington, DC.
authors.forename: Robert M
authors.initials: RM
authors.lastname: Post
authors.affiliation: Department of Psychiatry, VU University Medical Center, Amsterdam, the Netherlands.
authors.forename: Ralph
authors.initials: R
authors.lastname: Kupka
authors.affiliation: Department of Psychiatry & Behavioral Neuroscience, University of Cincinnati College of Medicine, Ohio, USA.|Lindner Center of HOPE, Mason, Ohio, USA.
authors.forename: Paul E
authors.initials: PE
authors.lastname: Keck
authors.affiliation: Lindner Center of HOPE, Mason, Ohio, USA.|Biological Psychiatry Program, University of Cincinnati Medical College, Ohio, USA.
authors.forename: Susan L
authors.initials: SL
authors.lastname: McElroy
authors.affiliation: Department of Psychiatry and Biobehavioral Sciences, David Geffen School of Medicine, University of California, Los Angeles.|Department of Psychiatry, VA Greater Los Angeles Healthcare System, West Los Angeles Healthcare Center, California, USA.
authors.forename: Lori L
authors.initials: LL
authors.lastname: Altshuler
authors.affiliation: Department of Psychiatry and Psychology, Mayo Clinic, Rochester, Minnesota, USA.
authors.forename: Mark A
authors.initials: MA
authors.lastname: Frye
authors.affiliation: Bipolar Collaborative Network, Bethesda, Maryland, USA.
authors.forename: Michael
authors.initials: M
authors.lastname: Rowe
authors.affiliation: Newcastle University, Institute of Neuroscience & Campus of Aging and Vitality, Wolfson Research Centre, Newcastle upon Tyne, United Kingdom.
authors.forename: Heinz
authors.initials: H
authors.lastname: Grunze
authors.affiliation: Department of Psychiatry and Behavioral Sciences, Stanford University School of Medicine, Palo Alto, California, USA.|VA Palo Alto Health Care System, Palo Alto, California, USA.
authors.forename: Trisha
authors.initials: T
authors.lastname: Suppes
authors.affiliation: Bipolar Collaborative Network, Bethesda, Maryland, USA.
authors.forename: Gabriele S
authors.initials: GS
authors.lastname: Leverich
authors.affiliation: University of Groningen, University Medical Center Groningen, the Netherlands.
authors.forename: Willem A
authors.initials: WA
authors.lastname: Nolen
mesh_terms: D000328:Adult; D017668:Age of Onset; D001714:Bipolar Disorder / Q000453:epidemiology*; D015988:Cohort Effect; D005190:Family; D005260:Female; D005858:Germany / Q000453:epidemiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D009426:Netherlands / Q000453:epidemiology; D012042:Registries; D014481:United States / Q000453:epidemiology