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Familial Resemblance in Religiousness in a Secular Society: A Twin Study

Personal religiousness such as praying to God, believing in God, and finding strength and comfort in religion were more influenced by genetic factors than were social forms of religiousness such as church attendance.

It is well known that human behavior and individual psychological traits are moderately to substantially heritable. Over the past decade, an increasing number of studies have explored the genetic and environmental influence on religiousness. These studies originate predominantly from countries generally considered more religious than the very secular northern European countries.

Comparisons of the results are complicated by diverse definitions of religiousness, but several studies indicate that the influence of the family environment is most predominant in early life, whereas genetic influences increase with age. We performed a population-based twin study of religiousness in a secular society using data from a Web-based survey sent to 6,707 Danish twins born 1970-1989, who were identified in the Danish Twin Registry. We applied Fishman's three conceptual dimensions of religiousness: cognition, practice, and importance. In all polygenic models and biometric analyses, we controlled for gender and age. The study sample comprised 2,237 same sex twins, a response rate of 45%.

We found high correlations within both monozygotic and dizygotic twin pairs in most items of religiousness, indicating a large influence from shared environmental factors. Personal religiousness such as praying to God, believing in God, and finding strength and comfort in religion were more influenced by genetic factors than were social forms of religiousness such as church attendance. We found a small tendency for increasing genetic influence with increasing age for some religious items, but not for all.

Table: Demographic and Number of Twins Answering Yes to Questions About Religiousness.

 

MZ female

DZ female 

MZ male

DZ male

Demographics        
 Invited  1.316  1.405  962 1.228 
 Participated 709 (54%) 672 (48%) 401 (42%) 455 (37%)
 Age (mean) 30,4  28,5  29,6  28,6 
 Member of the national church 618  551  313  358 
 Member of other churches   25    26     2     7 
 Not a member   66   95    83    90 
Cognition        
 I believe in God 290 218  116  117 
 I believe in life after death 276  246    92  115 
Practice        
 I go to church monthly   40    38    23    27 
 I pray to God 403  344  150  168 
Importance        
 God is important in my life 167  143    58    68 
 I find strength and comfort in religion 211  153    68    83 

 

Original publication:

Dorte Hvidtjørn, Inge Petersen et al.
Familial Resemblance in Religiousness in a Secular Society: A Twin Study
Twin Research and Human Genetics; 2013 Feb 22:1-10. Pubmed abstract