Structural brain abnormalities in first-degree relatives of patients with bipolar disorder or schizophrenia
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Patients suffering from either the severe mental disorder bipolar disorder (BD) or schizophrenia (SCZ) show resemblance in cognitive impairments, genetic etiology and structural brain abnormalities. Mapping the structural brain abnormalities in first-degree relatives of BD and SCZ patients can be valuable in order to elucidate the causes of brain abnormalities observed in the patients themselves. The first aim of this thesis is to provide an overview of brain volume abnormalities found in first-degree relatives of BD and SCZ patients. It will also be studied whether there are differences in structural brain abnormalities between siblings, parents, co-twins and offspring of either BD or SCZ probands. Furthermore, the differences in brain volume abnormalities of first-degree relatives of BD patients and first-degree relatives of SCZ patients will be studied. Thirty-two studies investigating structural brain abnormalities in first-degree relatives of BD patients, and three reviews and two meta-analyses investigating structural brain abnormalities in first-degree relatives of SCZ were examined here. From the overview that arose from these articles a list is made of brain regions that were in more than one study found to have an abnormal volume in first-degree relatives compared to healthy controls. It appeared that in first-degree relatives of BD patients there is little consistency in the findings of these studies, with the exception of a rather consistent reported decrease in prefrontal cortex volume. Differences in structural brain abnormalities between siblings, parents, co-twins and offspring of BD probands could not be identified. Decreased hippocampus and prefrontal cortex volumes and increased third ventricle volumes have been consistently reported in all sub-groups of first-degree relatives of SCZ patients. Parents of SCZ patients are also likely to have decreased insula volumes. Although not all results are consistently found, it can be stated that there are more structural abnormalities in the first-degree relatives of SCZ patients than in those of BD patients. Because of the large amount of research already conducted in first-degree relatives of SCZ patients resulting in rather consistent findings for these subjects, in the future it might be valuable to increase the amount of research conducted on structural brain abnormalities in first-degree relatives of BD patients in order to achieve more consistent results in these subjects.