The Role of Psychiatric Medication in Brain Structure in Bipolar Disorder Patients

This thesis describes the relationship between bipolar disorder and brain structure. One of the recurrent findings in this thesis is that the group differences in brain structure may be attenuated by lithium use and lithium has a normalizing effect on both grey matter and white matter microstructure. This hypothesis is strengthened by the analyses in which patients on and off lithium were separately compared with controls. In contrast, the associations between antipsychotic medication and brain structure are weak.

A second finding was that the relationship between brain structure and IQ did not differ between bipolar disorder patients and controls. We investigated total brain, subcortical and local cortical volume and white matter microstructure. Although we do report that total brain volume and superior temporal volume mediated the relationship between diagnosis and IQ, this explains only a small part of the variation and therefore can only partially contribute to the IQ deficits in patients with bipolar disorder. This means that other disease related factors probably contribute to the lower IQ after disease onset.

Whether the illness-related brain abnormalities can be explained by aberrant neurodevelopment, the presence of psychosis, or other processes specific to bipolar disorder needs further investigation. It would be particularly interesting to evaluate the effects of different treatments over the course of illness in longitudinal studies.