Circadian Typology: A Comprehensive Review

Abstract

The interest in the systematic study of the circadian typology (CT) is relatively recent and has developed rapidly in the two last decades. All the existing data suggest that this individual difference affects our biological and psychological functioning, not only in health, but also in disease. In the present study, we review the current literature concerning the psychometric properties and validity of CT measures as well as individual, environmental and genetic factors that influence the CT. We present a brief overview of the biological markers that are used to define differences between CT groups (sleep–wake cycle, body temperature, cortisol and melatonin), and we assess the implications for CT and adjustment to shiftwork and jet lag. We also review the differences between CT in terms of cognitive abilities, personality traits and the incidence of psychiatric disorders. When necessary, we have emphasized the methodological limitations that exist today and suggested some future avenues of work in order to overcome these. This is a new field of interest to professionals in many different areas (research, labor, academic and clinical), and this review provides a state of the art discussion to allow professionals to integrate chronobiological aspects of human behavior into their daily practice.

Keywords:

• Age
• Circadian typology
• Chronotype
• Cognitive performance
• Morningness–eveningness
• Personality
• Psychiatric disorders
• Sex
• Shiftwork

Acknowledgements

The authors thank Prof. Yvan Touitou for considering the importance of the issue and for providing an opportunity for this review to be published in Chronobiology International.

Declaration of Interest: The authors report no conflicts of interest. The authors alone are responsible for the contents and writing of the paper.

A.A. was supported by a grant from the Spanish Ministry of Science and Innovation (PSI2009-12300), S.N.A. was supported by grants from the BBSRC (BB/F022883/1) and AFOSR (FA-9550-08-1-0080), M.P.H. was supported by a grant from CAPES, CNPq, FAPERGS and FIPE/ HCPA-Brasil and C.R. was supported by a sabbatical leave.