Øjvind Lidegaard1, Professor, DMSci
ORCID: 0000-0002-7071-5496
Word count abstract: 222 words
Word count main text: 2486 words
Number of tables: 2
Number of figures: 0
Department of Gynaecology, Rigshospitalet, University of Copenhagen,
Denmark
Department of Clinical Medicine, University of Copenhagen, Copenhagen,
Denmark
Abstract
Background. Recently three large-scale epidemiological
registry-based Scandinavian studies examined the association between use
of hormonal contraception and the risk of developing depression or use
of antidepressants. They reached surprisingly divergent results.
Objectives: The aim of this study was to explain why
these three recent studies from Denmark and Sweden could achieve quite
different results, interpretations, and conclusions.
Methods: Search strategi and selection. The three existing large
scale Scandinavian studies examining associations between exposure to
different types of hormonal contraception and risk of depression or use
of antidepressants were examined according to chosen design, exclusion
criteria, and included confounders. Methodological choices were
considered, and the validity of these methodological choices tested.
Main results. First, the assumption that differences
between studies are due to residual confounding is proven unlikely,
already because confounder control beyond age, year and education rarely
change estimates materially. More likely basic differences in chosen
study groups, exclusions from the study groups, exposure definitions,
chosen reference populations, and interpretation of the results seem to
explain the differences between the studies.
Conclusion. The detailed review of the three
Scandinavian studies reveals methodological choices as the main
explanation for their different findings. Residual confounding was found
unlikely to explain the divergent results, while ideological
circumstances might have a main responsibility for the different chosen
methods and for the interpretation of the results.Funding. None.Key words: hormonal contraception, depression, oral
contraceptives, antidepressant drugs