Month of birth and mood seasonality: A comparison between countries in the northern and southern hemispheres
Article first published online: 15 APR 2013
© 2013 The Authors. Psychiatry and Clinical Neurosciences © 2013 Japanese Society of Psychiatry and Neurology
Psychiatry and Clinical Neurosciences
Volume 67, Issue 3, pages 133–138, April 2013
How to Cite
Tonetti, L., Milfont, T. L., Tilyard, B. A. and Natale, V. (2013), Month of birth and mood seasonality: A comparison between countries in the northern and southern hemispheres. Psychiatry and Clinical Neurosciences, 67: 133–138. doi: 10.1111/pcn.12036
- Issue published online: 15 APR 2013
- Article first published online: 15 APR 2013
- Manuscript Accepted: 13 JUN 2012
- Manuscript Revised: 11 JUN 2012
- Manuscript Received: 6 JUL 2011
- cross-cultural comparison;
- seasonal affective disorder;
- young adult
A previous study has reported a significant month-of-birth effect on mood seasonality in the northern hemisphere. Higher mood seasonality was observed for university students born during spring or summer months (long photoperiod) compared to those born during autumn or winter months (short photoperiod). The aim of this study was to test the hypothesized photoperiod effect by comparing the correlation between month of birth and mood seasonality in two countries located at the opposite poles of the terrestrial globe: Italy (northern hemisphere) and New Zealand (southern hemisphere). On the basis of the photoperiod-at-birth hypothesis, we expected to find higher mood seasonality among individuals born in months with longer photoperiods in both countries.
The Seasonal Pattern Assessment Questionnaire was administered to 1514 young adults (1088 women, 426 men; 1027 Italians, 487 New Zealanders), with ages ranging from 18 to 34 years. The Global Seasonality Score, which is a measure of mood seasonality, was calculated from the Seasonal Pattern Assessment Questionnaire.
A significant overall month-of-birth effect was observed on the Global Seasonality Score, but only for men. Men born in April and August (corresponding in Italy to a long photoperiod, in New Zealand to a short photoperiod) had higher mood seasonality than those born in February, regardless of country.
A significant month-of-birth effect was found on mood seasonality, but results do not support the hypothesis based on the photoperiod effect.