Electromagnetic radiation influences in many ways humans and animals, while earthquakes are known to be related with electromagnetic phenomena. We recently showed that large earthquakes reduced admissions of psychiatric patients, whereas small earthquakes were associated with increased number of admissions. Our aim was to examine the effect of seismic-related electromagnetic activity on two chronic and severe psychiatric disorders varying in terms of etiology and treatment, i.e. bipolar disorder and schizophrenia. Retrospective data concerning monthly admission rates of patients diagnosed with schizophrenia or bipolar disorder in the Psychiatric Unit of the University Hospital of Heraklion, Crete, Greece between 2008 and 2010 were analyzed in relation to the number of earthquakes with small (≥2) or larger magnitude in the Crete region in Greece. Results showed a marked reduction of acute admissions during a storm of large earthquakes, which was greater in patients with bipolar disorder (91.2%) than schizophrenia patients (52.4%). In addition there was a significant increase of admissions during a period of frequent small earthquakes, primarily among patients with bipolar disorder. The results suggest that electrostatic fields that accompany large earthquakes may have a protective effect on psychiatric disorders, particularly on bipolar disorder. These findings are consistent with the ameliorating effect of electromagnetic fields used in Electroconvulsive therapy (ECT) and Transcranial Magnetic Stimulation (TMS) in patients with bipolar disorder. Future studies focusing on the underlying mechanisms may lead to more specific treatments of psychiatric disorders.