Winter births have been associated with a higher risk of Alzheimer's disease (AD) and other psychiatric disorders. In the present investigation, this putative association was examined in a sample of gerontopsychiatric patients. An analysis of the quarterly birth rates of 83 patients with AD, 78 elderly depressive patients with an early onset and 74 patients with a late onset of the depressive disorder, 48 patients with both AD and depression (co-morbid patients) and 107 healthy control subjects, revealed no particular seasonal distribution for any of the diagnostic groups. In AD and co-morbid patients, controlling for the ApoE genotype did not change this finding. Logistic regression analysis revealed the expected findings that increasing age and the presence of the ApoE4 allele were associated with a higher risk of dementia. Younger age and female gender were identified as risk factors for a depressive disorder. A winter birth (birth in the first three months of the year) was not associated with any of the diagnostic subgroups. We concluded that in our sample a seasonal distribution of births was not found to increase the risk for AD or geriatric depression.