Does latitude as a zeitgeber affect the course of bipolar affective disorder?

It has been increasingly recognized that circadian rhythm abnormalities could play an important role in the relapse and symptom expression of bipolar disorder. The mania predominance in the course of BD in this population contrasts from the depressive predominance in other studies. We suggest that this phenomenon could be a function of latitudinal gradient in the expression of BD using the zeitgeber hypothesis.