APOLIPOPROTEIN-E - DEPRESSIVE-ILLNESS, DEPRESSIVE SYMPTOMS, AND ALZHEIMERS-DISEASE

Background: The apolipoprotein E (ApoE) epsilon 4 and epsilon 2 allele s may influence the age of onset of depressive illness. Depressive ill ness of late onset is also a risk factor for Alzheimer's disease (AD), and there is some evidence that the ApoE epsilon 2 allele is associat ed with depressive symptomatology in AD, Depressive symptomatology in AD may thus share common genetic risk factors with late-onset depressi ve illness. Methods: The frequency of the epsilon 2 and epsilon 4 alle les of ApoE and their effects on age of onset of disease in three inde pendent groups of subjects, with depressive illness, with AD, and cont rols, were compared in a defined population from Southeast London. Res ults: The frequency of the ApoE epsilon 2 allele was significantly low er in the depressive illness group compared with the control group and was associated with a later mean age at onset. Subjects with depressi ve symptomatology in AD had a higher frequency of the ApoE epsilon 2 a llele and had a significantly later age of onset of depressive illness compared with the nondepressed AD group. Conclusions: The presence of the ApoE epsilon 2 allele in AD is found to be highly associated with depressive symptomatology, and it is proposed that this subgroup repr esents the presence of delayed depressive illness and that there are c ommon genetic risk factors between AD and depressive illness. (C) 1998 Society of Biological Psychiatry.