By Mark Cowen, Senior medwireNews Reporter
Conversion from bipolar disorder not otherwise specified (BD-NOS) to a diagnosis of bipolar I (BD I) or II (BD II) disorder is common among children, research confirms, and is predicted by a family history of mood disorders.
In a study of 27 children, aged 6-12 years, with a diagnosis of BD-NOS, the team found that 33% converted to a diagnosis of BD I (n=8) or BD II (n=1) over a follow-up period of 18 months.
Children with a family history of mood disorders in first-degree relatives were over twice as likely to covert as those without such a family history.
The findings, published in the Journal of Affective Disorders, "further indicate both the instability of the BD-NOS diagnosis as well as its common progression to a well-established bipolar diagnosis," say Mary Fristad and Molly Martinez from Ohio State University in Columbus, USA.
Of the children who converted to BD I or BD II, five converted within 6 months of initial diagnosis, three more converted by 12 months, and one more converted by 18 months.
Six (46.2%) of 13 children who had a first-degree relative with bipolar disorder symptoms converted compared with just three (21.4%) of 14 children without such a family history, at a relative risk (RR) of 2.19.
Similarly, six (50.0%) of 12 children with a "loaded pedigree" (three or more first- or second-degree relatives) for depression diagnosis converted compared with just three (21.4%) of 14 children without, at an RR of 2.34.
In addition, six (42.9%) of 14 children with a multigenerational family history (three consecutive generations) of depression diagnosis converted compared to just three (25.0%) of 12 children without, at an RR of 1.72.
Fristad and Martinez conclude: "This study replicates the previous finding of a high rate of conversion from BD-NOS to BD-I or II among youth, and suggests conversion is related to symptoms of bipolar disorder or depression diagnoses in the family history."
However, they acknowledge that "this study's major limitation is the small sample size," adding that "additional research is warranted in a larger sample with a longer follow-up period."
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