Further Evidence of a Cohort Effect in Bipolar Disorder

Abstract

Objective: 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. Methods: 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. Results: 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). Conclusions: 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.

The Challenges of Children with Bipolar Disorder

“…Other data indicate a similar percentage of bipolar I children in other countries, but if those with BP-NOS are considered, the incidence may be considerably higher, perhaps around 5%. Childhood onsets of bipolar disorders are more common in the US than in many European countries with one quarter of onsets in adults with bipolar disorder occurring before age 13 and two thirds before age 19 [2][3][4][5] Multiple factors account for this; among the most prominent are an increased incidence of a positive family history of mood disorders and substance abuse disorders in patients' parents and grandparents [6][7][8] and an increased incidence of multiple psychosocial adversities (different types of abuse) in childhood [9]. There are additive effects on earlier age on onset when there is the combined presence of both a high loading of family history and incidence of childhood adversity [7].…”

Bipolar II Disorder: Not So Sure It Is Time for Something New

“…However, some twothirds of women and about 40% of men experience it as dysphoric, filled with anxiety and feeling pressured, agitated, and irritable, and do not like it all. 7 Blaming the apparent recent increase in the diagnosis of BP II on the pharmaceutical industry seems a little lame, especially since a cohort effect for both unipolar and bipolar disorder, as well as attention-deficit hyperactivity disorder and substance abuse, has been demonstrated over many generations, 8,9 although Parker and Fletcher 10 did see a bigger effect for BP II than BP I patients.…”

How to prevent the malignant progression of bipolar disorder

“…The problems of early-onset illness will only continue to worsen as data indicate the presence of a cohort effect for depression, bipolar disorder, and substance abuse. 31 , 32 …”