A study of depressed patients with subjective memory complaints: A volumetric MRI study of the hippocampus and the amygdala

Subjective memory complaints are common in depression and not closely related to performance on memory tests. The possibility that hippocampal and amygdalar abnormalities may be related to subjective memory problems in these patients has not been explored. This study investigates volumetric changes in the hippocampus and the amygdala in depressed, non-demented patients with persistent cognitive complaints. Methods. Fourteen non-demented patients who fulfilled ICD-10 criteria for depression and who persistently complained of "memory" difficulties were studied. They had been tested neuropsychologically when first referred to the National Hospital for Neurology and Neurosurgery on average three and a half years before this study. Volumetric magnetic resonance imaging (MRI) was performed in 1998 and neuropsychological testing repeated. Fourteen healthy volunteers with no history of psychiatric illness matched for age and gender were used as controls for MRI data. Volumetric measurements of amygdala and hippocampus were performed blind to side and group membership. Results. Five patients had intellectual or memory underfunctioning when first tested, but all had improved or returned to normal by the time of the study. The volume of the left amygdala was significantly smaller in patients compared to controls. In the five patients with initial neuropsychological impairment the volume of the left hippocampus tended to be smaller than in the unimpaired. Seven patients still complained of memory difficulties at the time of the study and this was unrelated to objective neuropsychological performance. Conclusions. The study suggests that subjective memory complaints in depression are not a harbinger of dementia. The reduction of amygdalar volume observed in these patients is more likely to be related to depression and subjective memory complaints than to cognitive impairment, but may be relevant to the both. Changes in hippocampal volume may be more closely related to the subtle cognitive impairment observed and to subjective memory loss