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Epigenetic processes may link childhood maltreatment and bipolar risk

By Lucy Piper, Senior medwireNews Reporter

12 June 2013

medwireNews: Childhood maltreatment may have a sustained effect on the hypothalamic-pituitary-adrenal (HPA) axis, which could alter brain development and increase the risk for bipolar disorder, study findings suggest.

In a group of 99 patients with bipolar disorder, researchers found that those reporting lots of different types of childhood maltreatment were more likely than those reporting no childhood trauma to have a high percentage of methylation in the promoter region of the glucocorticoid receptor gene (NR3C1) in blood lymphocytes, an effect that could be measured in the peripheral blood.

"This suggests that epigenetic processes, through enduring alteration of the HPA axis, may mediate the impact of early-life adversities on adult psychopathological disorder," say Nader Perroud (University Hospitals of Geneva, Switzerland) and colleagues.

Among the 99 participants, a high percentage reported childhood maltreatment, including sexual abuse (30%), physical abuse (33%), physical neglect (29%), emotional abuse (48%), and emotional neglect (56%).

Replicating their previous findings in patients with borderline personality disorder, the researchers found that higher numbers of childhood maltreatments were significantly associated with higher percentages of NR3C1 methylation.

Also, the percentage of NR3C1 methylation was significantly and independently associated with the severity of each type of maltreatment. The most significant association was with emotional abuse.

"This highlights the importance of the caregiving function at early age and the fact that early-life alterations in the attachment process may produce long-lasting biological consequences," the researchers comment in The British Journal of Psychiatry.

They note that the number of childhood maltreatment events in their group of bipolar disorder patients correlated with bipolar II disorder and a history of substance and alcohol use disorder.

Although the small sample size makes firm conclusions difficult, the researchers say their results "suggest that childhood trauma may change the course of bipolar disorder towards a type 2 disorder with comorbid substance use disorder, possibly through altered HPA axis functioning."

Perroud et al call for further studies to "improve the definition of clinical and environmental characteristics of patients in order to finely match epigenetic modifications with individual outcomes."

medwireNews (www.medwirenews.com) is an independent clinical news service provided by Springer Healthcare Limited. © Springer Healthcare Ltd; 2013

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