Increased hippocampal volumes in lithium treated adolescents with bipolar disorders: a structural MRI study.

Background: Structural neuroimaging studies in bipolar disorder (BD) have consistently identified several anatomical abnormalities in many brain areas related to mood regulation. Hippocampus is one of the key components of emotional regulatory networks in the brain. Evidence about hippocampal changes in BD is quite limited and inconsistent particularly for adolescent onset BD. It is aimed to compare hippocampus volumes of euthymic BD-I adolescents with healthy controls using structural MRI.

Methods: Hippocampal volumes of seventeen youths between 13 and 19 age period with DSM-IV BD (seven boys) and twelve healthy comparison subjects (five boys) were compared using structural MRI. Differences in hippocampal volumes between groups were tested.

Results: There was no significant difference between the right and left hippocampus volumes of patients with BD and the control group. However boys tended to have significantly larger right hippocampal volumes than girls both in BD and control group. Right hippocampal volumes were enlarged in lithium treated bipolar patients. This enlargement is not related to sex.

Limitations: Future, longitudinal follow-up studies need large enough sample sizes of both sexes and a sex-matched healthy comparison group to sort out developmental, gender and medication influences on brain structures over time in BD.

Conclusions: Lithium treatment in adolescent-onset BD has a significant effect on hippocampus volumes.