The question may sound strange and alleged link far-fetched,
but several scientific studies claim that there is a substantial correlation
indeed, confirming that the children born of older parents have higher risk of
psychological disorders, including depression over the lifetime.
Mother's Age and
Depression Symptoms in Daughters
New research from the University of Western Australia
suggests that the daughters of women who give birth at the age 30 or older are
more likely to experience symptoms of depression as young adults.
"This study suggests that older maternal age is
associated with symptoms of depression, anxiety and stress in young adult
females," Jessica Tearne, a doctoral student and lead author of the study,
said in a statement.
For the study, researchers collected and analyzed data
from the Western Australian Pregnancy Cohort (Raine) Study. Researchers found
that daughters of women who were 30 to 34 when they gave birth had higher
levels of stress and those whose mothers were over age 35 at the time of birth
had significantly higher levels of stress, depression and anxiety compared with
daughters whose mothers were under age 30. Women who were under 20 years old
when they gave birth did not have an effect on their offspring. Researchers
found that the fathers' age at the time of birth also had no effect, and there
was no effect found for sons.
"One hypothesis is difficulties may occur in the
mother-daughter relationship because of a large age difference between the
two," Tearne said. "It may be that a 30 or more year age difference
between mother and daughter leads to a significant difference in the value
systems that may cause tensions in the relationship, leading to stress, worry
and sadness in the child, particularly during the transition to young
adulthood."
Another possible explanation may be that the women who
gave birth over age 30 would be in their 50s at the time their children were
assessed and therefore more likely to be experiencing health problems
associated with aging. Tearne said this could lead to higher levels of symptoms
in the children.
Father’s Age and Psychological
Problems in Children
The risk of bipolar
disorder ("manic depression") particularly for early-onset disease,
is J-shaped, with the lowest risk for children of 20- to 24-year-old fathers, a
twofold risk for younger fathers, and a threefold risk for fathers >50 years
old. There is no similar relationship with maternal age (Wikipedia).
While a mother's age is often considered a genetic risk
factor for offspring, the recent research also pointing the finger at fathers,
too—particularly when it comes to the mental health of their progeny. Males may
have the advantage of lifelong fertility, but as they grow older, the rate of
genetic mutations passed on via their sperm cells increases
significantly—putting their children at increased risk for psychiatric
disorders, including depression. Two recent studies support this link at least
associatively, but experts remain uncertain if age is the cause of these
problems.
The Malaysian Mental Health Survey (MMHS) results, which
were published online in March 2011, for instance, revealed that people with older
parents as well as those whose fathers were at least 11 years older than their
mothers, were at increased risk for certain mental health disorders, including
anxiety, depression, obsessive-compulsive disorder and phobias. Offspring whose
fathers were 19 or younger when the child was born had just a 9 percent
prevalence of mental health disorders. Regardless of paternal age, however, if
the father was 11 years or older than the mother, that rate jumped to 24
percent. The greatest risk of mental health disorders—42 percent—was seen in
the children of fathers aged 50 and older, with wives at least 11 years younger,
than their husbands were.
Has the sperm gone bad? Some researchers disagree about
whether the connection between paternal ages is purely based on internal
genomic mechanisms related to the aging process, aka "sperm gone
bad," or whether environmental and epigenetic factors also affect
outcomes.
"The links between a father's age and mental
outcomes is multifactorial. You have to take into consideration epigenetic,
psychosocial and biological factors," says John McGrath, a professor of
psychiatry of the Queensland Brain Institute at the University of Queensland in
Australia.
The epigenetic approach is based on the theory that
accumulated exposure to environmental toxins over time causes genetic
expression alterations that are passed on to later generations and lead to
disease in the children later in life. For example, children of Vietnam War
veterans exposed to the herbicide agent orange have an increased risk for spina
bifida due to epigenetic changes. And drinking and smoking can have epigenetic
effects in offspring.
Likewise, a psychosocial approach focuses on external
factors that might contribute to the expression of certain genes. "Delayed
paternity does increase the risk of mental disorders, but genetic mutations may
not be causative," MMSE researcher Kavitha Subramaniam said in a prepared
statement. "They may behave more like susceptibility factors, so that
children of older fathers may overreact and show phenotypic expression of
certain diseases when they face environmental stimuli. Whereas those with no
genetic liability may not develop mental health disorders."
Nevertheless, the effect of aging on gene expression is
still considered the primary force driving mental health outcomes in the
children of older men. Advancing paternal age is associated with spontaneous
mutations—changes in the nucleotide sequence of a chromosome. The older men
get, the more vulnerable their sperm becomes to such spontaneous genetic
mutations.
When it comes to reproductive outcomes, older men are
actually disadvantaged compared with older women, due to the high rate of sperm
cell division. McGrath points out that during a woman's lifetime, her oocyte
cells divide only 23 times. Women are born with all of the eggs they will ever
carry. Once boys hit puberty, their sperm cells divide every 16 days. "By
the time a man is 40, his sperm cells have undergone 660 cell divisions, and
800 cell divisions by age 50," he says. More divisions translate into a
higher risk for genetic alterations.
So at what paternal age does the risk of mental health
disorders among offspring increase significantly? The evidence varies.
In a meta-analysis published online in November 2010
Christina Hultman, an epidemiologist at the Karolinska Institute in Stockholm,
found that men between the ages of 40 and 49 were 1.4 times more likely to have
children with a diagnosis of autism than 15- to 29-year-old men—the reference
group for this study. Moreover, the risk of autism increased dramatically with
the father's age: Between the 50 and 54, men were 2.2 times more likely to have
children with a diagnosis of autism compared with the reference group; for men
aged 55 and above, comparative risk was 4.4 times greater than the control.
Another study, published online in April 2011, looked at
mental health outcomes in the children of fathers aged 40 and above in the
Netherlands. With more than 71,000 subjects this research, led by Jacobine
Buizer-Voskamp of the Rudolf Magnus Institute of neuroscience at the University
Medical Center Utrecht in the Netherlands, was the first large-scale, population-based
study to look at the effect of paternal age on four main psychiatric
diagnoses—autism spectrum disorder, schizophrenia, major depressive disorder
and bipolar disorder.
The researchers found that fathers aged 40 and above are
3.3 times more likely than under-40 fathers to have children with autism
spectrum disorder, whereas men aged 35 and older are 0.27 percent more likely
to have children who eventually develop schizophrenia, compared with men under
35.* The study did not show any connection between paternal age and bipolar
disorder. In the case of depression, the rate was higher not only in the
children of men over 40, but also in fathers aged 20 and younger—so it appears
that there are different biological and psychosocial mechanisms that influence
risk of affective disorders versus risk for autism spectrum disorder and
schizophrenia.
These findings led Buizer-Voskamp and her colleagues to
conclude that the association between paternal age and increased risk of autism
spectrum disorder may be a function of self-selection as well as genetics, in
which men with autistic tendencies tend to marry later, have children later and
pass on those traits to their offspring. Emerging research shows that social
function in people with autism spectrum disorder improves, as they get older,
which leads them to later marriage and older first-time parenthood. When they
finally have children, they pass on their genes for autistic tendencies. In
contrast, men with bipolar disorder during the pre-morbid phase tend to have
improved social and cognitive functioning, so they have no problem getting into
relationships and having children at a younger age.
McGrath disagrees with this theory regarding autism
spectrum disorder. "That's what I would call a systematic bias," he
says. "The idea that dad is weird and the kids are going to get his weird
genes has been around for some time, but the evidence suggests there is more
going on."
The emergence of this data represents a rare convergence
of two fields—genetics and epidemiology, McGrath says. "In epidemiology,
we see a higher risk of autism and schizophrenia in the children of older
fathers," he says, "while genetically, the focus is on copy number
variants and structural variations that could be linked to increased risk of
schizophrenia and autism."
Although this convergence is interesting, it is also
cautionary for men over 40 who want to start families or have more children.
Experts, however, offer some reassurance: "Late fatherhood is a secular
trend across many nations," McGrath says. "We all know older fathers
whose children turn out just fine."
In fact, Malaspina points out that duration of marriage
and being "wanted" (rather than the result of an unplanned pregnancy)
are two factors that seem to be protective against the development of
schizophrenia in the children of older men. "Based on research I did in
2001, being wanted reduces the risk of schizophrenia threefold in these
children," she says.
Sources and Additional Information:
