An overview of the demographic characteristics is given in t1. Patients with a first episode of major depression did not differ significantly from healthy comparison subjects with respect to age, gender, handedness, education, height, weight, and alcohol consumption. Furthermore, these variables also did not significantly differ between both male and female patients with first-episode depression and their matched healthy comparison subjects. Male and female patients did not differ according to age, age at onset of illness, illness duration, or severity of depression, as measured by the CGI and the Hamilton depression scale. Additionally, there was no significant difference in total brain volumes between patients and comparison subjects.
The brain volumetric data are shown in t2. No significant main effects on hippocampal gray matter volume were found for diagnosis (F=0.001, df=1, 55, p=0.99). The interaction between diagnosis and gender was significant (F=5.25, df=1, 55, p<0.03). F2 depicts the individual values for men and women. Post hoc univariate ANCOVA revealed that male patients with a first episode of depression had a significantly smaller left hippocampal volume than the healthy male comparison subjects (F=6.36, df=1, 25, p<0.02), whereas the right hippocampal volume was not significantly different (F=0.12, df=1, 25, p=0.73). On the other hand, female patients with a first episode showed a tendency to have a significantly larger right hippocampal volume than female healthy comparison subjects (F=3.81, df=1, 33, p=0.06), whereas no significant differences were detected for the left hemisphere (F=1.66, df=1, 33, p=0.22). The main gender effect was significant, with male subjects having greater hippocampal gray matter volume than female subjects (F=8.34, df=1, 55, p=0.006). The hemisphere effect (F=5.58, df=1, 55, p=0.02) and the interaction of diagnosis and hemisphere (F=8.13, df=1, 55, p=0.006) were significant. Post hoc analysis revealed a significant left-right asymmetry in the first-episode patients (t=3.72, df=29, p=0.001), whereas the healthy comparison subjects did not show significant hemispheric differences (t=0.65, df=29, p=0.52) (F2). The interactions of hemisphere and gender (F=0.91, df=1, 55, p=0.34) and of diagnosis, hemisphere, and gender (F=1.10, df=1, 55, p=0.30) did not reveal significant effects. The statistical analysis for total hippocampal volumes showed nearly similar results, in comparison to hippocampal gray matter volumes.
Diagnosis had a significant effect on hippocampal white matter volumes (F=7.54, df=1, 55, p=0.008). First-episode patients with major depression exhibited a significantly smaller hippocampal white matter volume than healthy comparison subjects (F3). Furthermore, a significant main effect was found for hemisphere (F=6.11, df=1, 55, p<0.02), whereas the interactions of hemisphere and diagnosis (F=2.88, df=1, 55, p<0.10) and of hemisphere and gender (F=1.91, df=1, 55, p=0.17) were not significant. No significant main gender effect was found (F=0.54, df=1, 55, p=0.47).
Pearson’s correlations between age and hippocampal volumes were not significant for either healthy comparison subjects or patients with depression. Furthermore, age at onset of illness and illness duration were not significantly correlated with hippocampal volumes. Inclusion of the cofactor age in a partial correlation also did not produce a significant relationship between age at onset of illness or duration of illness and hippocampal volume.