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 In a large retrospective study, researchers looked at depression
diagnoses among more than 2.2 million people in Sweden and their
parents and found that genetic factors and household environment
contributed equally to odds that the illness would be “transmitted”
from parents to offspring.
The results - based on comparing adopted and biological offspring
from both intact and broken families - contradict many previous
findings from twin studies that suggested genetic predisposition
plays the larger role in the inheritance of depression, the authors
write in JAMA Psychiatry.
“Their sample sizes were much too small and not always
representative,” said lead author Dr. Kenneth Kendler, a professor
of psychiatry and human and molecular genetics at Virginia
Commonwealth University in Richmond.
“Adoption studies are probably the most powerful method available to
understand the mechanism of parent-offspring transmission,” Kendler
said by email. “An important feature of this study was our ability
to replicate the results from adoptive and biological parents by
findings from step- and not-lived-with parents. This increases
considerably our confidence in these findings.”
In 2015, almost 7 percent of all adults in the U.S., or an estimated
16.1 million individuals age 18 or older, reported having had at
least one major depressive episode in the past year, according to
the National Institute of Mental Health. The disorder is associated
with significant work, school and health problems, substance abuse
and an increased risk of death by suicide.
Using data collected from January 1960 through December 2016,
Kendler and his colleagues analyzed newly available Swedish primary
care registries, combined with hospital and psychiatric outpatient
records to trace treated major depressive disorder in parents and
offspring. They examined five types of families with various
combinations of biological or adoptive offspring, intact households,
and those with an absent father, a stepfather or both.
The new data indicating that genes are not destiny have a range of
implications for research, treatment and child-rearing, experts
said.
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“There’s been this huge move in biological psychiatry to look for
the genes involved in mental illness,” said Robert Klitzman, a
professor of clinical psychiatry and director of the masters of
bioethics program at Columbia University in New York City, who
wasn’t involved in the study.
“We need to push research money so we’re not looking exclusively at
genes, but spending sufficient time figuring out the best ways to
treat the psychosocial factors of depression,” Klitzman said in a
telephone interview. “This study provides strong evidence to support
public policy for covering mental health treatment that includes a
combination of drugs and therapy.”
The study’s data highlight that when a mother’s mental health
suffers, so does her child’s, said Dr. Joan Luby of Washington
University School of Medicine in St. Louis, who wasn’t involved in
the research.
“If you have a genetic risk for depression you would be wise to
enhance certain elements of the child-rearing environment to protect
against transmission of depression,” Luby said in a phone interview.
“I personally think it has a lot to do with helping children develop
emotionally. They should learn how to experience, process and
regulate their emotions as opposed to sweeping them under the rug.”
Among the study’s limitations, the authors note, is that it is based
on registries of people with major depression, which may not
represent other groups. Some of the data also are self-reported,
meaning it may include “false-negative or false-positive” diagnoses.
Klitzman also pointed out that the data are from Sweden and may not
necessarily be similar in the U.S.
SOURCE: http://bit.ly/2z9C4Qx JAMA Psychiatry, online December 13,
2017.
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