Cortical thickness and psychosis: A family study

Background. Cortical thinning in schizophrenia has now been reported in several studies and seems to be a sensitive measure to identify small cortical lesions affecting distributed neurocircuits. However, studies investigating cortical thickness in relatives of patients with schizophrenia are scarce. This study examines whether decreased cortical thickness is an indicator of genetic liability for the disorder. Methods. T1-weighted MRI scans were acquired on a 3 Tesla scanner from patients with schizophrenia, their healthy siblings and controls. Brain Voyager QX was used to measure cortical thickness using the Laplace method in a preliminary study sample of 10 patients with schizophrenia, 10 non-psychotic siblings of these patients and 10 control subjects. Group analyses were performed in surface space after cortex based alignment of segmented cortices. Results. Preliminary whole brain analyses showed decreases in cortical thickness in the frontal lobe and occipital lobe but primarily in the inferior temporal lobe and inferior parietal lobe in patients compared to controls. Relatives showed cortical thinning in the posterior temporal lobe and in some regions of the frontal lobe compared to controls. When patients were compared with relatives, it was found that patients have less cortical thickness in the frontal lobe, occipital lobe, inferior parietal lobe and the temporal lobe. The results did however not reach the level of statistical significance after multiple comparison correction, which is probably due to lack of power in this preliminary sample. To increase statistical power a detailed patches of interest analysis was performed. Results revealed a trend towards decreases in cortical thickness in the right Collateral Sulcus in patients compared to controls. In the relatives, a trend towards cortical thinning in the right Cuneus and in the right transverse Occipital Sulcus was found. When patients were compared with relatives, patients appeared to have less cortical thickness in the right Collateral Sulcus and in the left Inferior Occipital Gyrus. Some increases in cortical thickness were found in the left Postcentral Gyrus in both patients and relatives compared to controls (p<0,05). Conclusion. Alterations in cortical thickness may be associated with the genetic liability for schizophrenia. More robust results from whole brain analyses and patches of interest analyses on a three times larger study sample will be presented.