Numerous studies have revealed correlations between psychoactive substance
use and other factors, but few have charted the underlying links from genetics
to church going, childhood upbringing, and adult experience.
In the latest of his many studies of several populations of twins, Kenneth
Kendler, M.D., shows how genes and environment influence church attendance and
use of alcohol and nicotine from childhood to adulthood.
Kendler is the Rachel Brown Banks Distinguished Professor of Psychiatry and
director of both the Psychiatric Genetics Research Program and Virginia
Institute for Psychiatric and Behavioral Genetics at the Virginia Commonwealth
University School of Medicine in Richmond.
When the twins in their study were young, they were most strongly
influenced by common parental and community expectations regarding church
attendance, wrote Kendler and John Myers, M.S., in the October American
Journal of Psychiatry. That influence virtually disappeared in adulthood,
when genetic influences on personality largely led to decisions about going to
church, with environmental factors not shared by the other twin playing an
important secondary role.
The new study included data from 1,795 Caucasian male twins in the Virginia
Adult Twin Study of Psychiatric and Substance Use Disorders. They were born
from 1940 to 1974 and were interviewed in two waves, 1993-1996 and 1994-1998.
Included were 469 monozygotic pairs and 287 dizygotic pairs. Over the course
of several interviews, researchers asked the twins about current and past
attendance at church or other religious services, how much and how often they
drank alcohol, and the average number of cigarettes a day (if any) they
Using sophisticated statistical models, Kendler and Myers found the
proportion of variance among the twins at ages 8 to 11, 12 to 14, and 15 to 17
and as adults with an average age of 40. They looked at three explanatory
factors: additive gene effects, shared environmental effects, and
individual-specific environmental effects.
In the youngest age group (8 to 11) and in early adolescence (12 to 14),
shared environment explained 50 percent of individual differences in church
attendance, a figure that dropped slightly to 41 percent in late adolescence
(15 to 17). However, the effect of that shared childhood environment accounted
for only a statistically insignificant 3 percent for the twins in
Meantime, the role of heritability in church attendance was 21 percent, 25
percent, and 38 percent over the three younger age ranges, but rose to 58
percent among the adults. Individual-specific environmental effects were
fairly stable in youth, from 21 percent to 28 percent, but accounted for 41
percent of church attendance among the adults.
Kendler and Myers next looked at the correlation between church attendance
and use of alcohol or tobacco. They hypothesized that church attendance served
as a marker for a constellation of negative attitudes toward alcohol and
tobacco use among the largely Protestant (85 percent) study participants.
Alcohol use at ages 12 to 14 was almost entirely (88 percent) due to a
shared environment. That proportion dropped to 51 percent in late adolescence
and to zero in the adults. Genetic factors were miniscule in early adolescence
(7 percent), rose to 49 percent in late adolescence, and 62 percent among
adults. Individual-specific environmental factors for the church
attendance/alcohol relationship were miniscule in youth but rose to 38 percent
The shared childhood environment also accounted for most of the level of
nicotine consumption at both stages of adolescence, with only a slight genetic
contribution. However, in adulthood, genetic factors accounted for 85 percent
of the correlation with church attendance, with the rest due to the
"[A]s individuals age, they increasingly shape their own social and
religious behavior in large part through their genetically influenced
temperament," wrote Kendler and Myers.
Thus, more than parents' wishes or advice, personal
temperament—mainly influenced by their offsprings'
genetics—directed the twins' choices in post-adolescent life: college,
careers, new friends, romantic partners. Those environmental factors in turn
played a role in everything from church attendance to smoking and
That understanding may ultimately have some clinical value, they suggested."
[T]he pattern of findings uncovered in these analyses can help inform
our efforts to prevent and reduce harmful consumption of psychoactive
"A Developmental Twin Study of Church Attendance and Alcohol
and Nicotine Consumption: A Model for Analyzing the Changing Impact of Genes
and Environment" is posted at<http://ajp.psychiatryonline.org/cgi/reprint/appi.ajp.2009.09020182v1>.▪