A volumetric MRI study of the hippocampus in type 1 and 2 alcoholism

In recent years, magnetic resonance imaging (MRI) of the hippocampus has been extensively studied on neurological and psychiatric disorders. Particularly in studies on schizophrenia and mood disorders, findings regarding the hippocampal involvement have been most controversial. Previously, minor volume loss of the hippocampus in alcoholism, a major comorbidity alongside psychiatric disorders, has been reported but no data exist on the hippocampal volumes in subtypes of alcoholism. In this study, MRI was used to measure volumes of the hippocampus in late-onset type 1 alcoholics and early-onset type 2 alcoholics. The type 2 alcoholic subjects were also violent offenders with antisocial personality disorder, derived from a forensic psychiatric sample. All were non-psychotic and legally competent. Normal volunteers, representing a wide age range, served as a controls group. Compared to the controls, the right, but not left, hippocampi were significantly smaller in both alcoholic groups. While there was no correlation between the hippocampal volumes with age in the control subjects, there was tendency towards decreased volumes with aging and also with the duration of alcoholism in the type 1 alcoholic subjects. Surprisingly, there was a significant positive correlation between the right hippocampal volume and age in the type 2 alcoholics. This study provides further in vivo evidence that type 1 alcoholism, in general, is associated with a minor loss in hippocampal volume. It is suggested that type 2 alcoholism, in general, similarly displays a minor decrease in hippocampal volume, but this decrease is unevenly distributed within the type 2 category, being weighted towards the younger subjects. These effects suggest differences between the two alcoholic groups, and raise the possibility that the observed effects within the type 2 category are due to other factors than the cumulative acquired effects related to alcohol abuse, such as primary personality psychopathology.