In the study, published by Jesse D. Eclarinel and colleagues in The FASEB Journal, pregnant mother rats were placed in cages that each contained an exercise wheel. One group had access to a working wheel on which they could run. The other group had the same wheel, but it was locked so that they couldn’t use it for running. Daughters of the rats who ran during pregnancy ran more in adulthood (both at 60 days and 300 days after birth) than daughters of the rats who couldn’t run during pregnancy.
While it is a mystery why this occurs, it is consistent with other data about the ways that a parent’s experiences can influence the next generation, even when the offspring don’t grow up with the parents.
For example, father rats conditioned to associate a specific smell with fear of an electric shock have offspring that also fear that smell (but not other smells).
Drug use is another example. Father rats given access to cocaine have offspring that are less interested in cocaine. Interestingly, father rats exposed to marijuana have offspring that are more interested in opiates.
Experiences with drugs or stress are thought to affect the next generation via ‘epigenetic’ marks on ova or sperm. These marks change the way DNA is packaged, with long-lasting effects on behavior and chemistry. Most marks from a mother’s or father’s experiences are erased at the time of conception, but some persist and affect the next generation.
The nature versus nurture debate is getting more and more complicated. Parents can influence offspring in a number of ways: 1) genetics; 2) epigenetics in the absence of contact between parent and offspring after birth; 3) epigenetic effects of behavioral contact—that is, parents’ caring and warmth versus abuse and neglect can affect offspring’s DNA expression too. All these are in addition to any purely behavioral influence a parent may have on their offspring via discipline, teaching, being a role model, etc.
Editor’s Note: The moral of the story is, choose your parents wisely, or behave wisely if you yourself become a parent.
For decades, researchers have known that a pregnant mother’s diet, hormone levels, and psychological state can affect her offspring’s development, altering organ structure, cellular response, and gene expression. It is now becoming clear that a father’s age and lifestyle at the time of conception can also shape health outcomes for his offspring.
Older fathers have offspring with more psychiatric disorders, possibly because of increased incidence of mutations in sperm.
A 2016 article by Joanna Kitlinska and colleagues in the American Journal of Stem Cells reviewed findings from human and animal studies about the links between fathers’ behaviors and their offspring’s development.
Father’s behavior can shape gene expression through a phenomenon described as epigenetics. Epigenetics refers to environmental influences on the way genes are transcribed. While a father’s behavior is not registered in his DNA sequences, it can influence the structure of his DNA or the way in which it is packaged.
Kitlinska suggests that these types of findings should eventually be organized into recommendations for prospective parents. More research is also needed into how maternal and paternal influences interact with each other.
Some findings from the article:
- A newborn can have fetal alcohol spectrum disorder even if the mother doesn’t drink. “Up to 75% of children with [the disorder] have biological fathers who are alcoholics,” says Kitlinska.
- Father’s alcohol use is linked to low birth weight, reduced brain size, and impaired cognition.
- Dad’s obesity is linked to enlarged fat cells, diabetes, obesity, and brain cancer in offspring.
- A limited diet in a father’s early life may reduce his children and grandchildren’s risk of death from cardiovascular causes.
- Dad’s advanced age is correlated with higher rates of schizophrenia, autism, and birth defects in his children.
- Psychosocial stress on dads can affect their children’s behavioral traits.
Researchers are looking for better ways of predicting whether children at risk for bipolar disorder will go on to develop the illness. A 2015 study by David Axelson and colleagues in the American Journal of Psychiatry reported that in the offspring of parents with bipolar disorder, diagnoses of sub-threshold mania, depression, and disruptive behavior disorders were associated with subsequent diagnosis of full-blown Bipolar I or Bipolar II disorders six to seven years later.
More recently, in an article by Danella M. Hafeman and colleagues in the American Journal of Psychiatry, the same group of investigators has examined how symptoms (rather than categorical diagnoses, as in the earlier study) predict the development of bipolar disorder. In children and adolescents at high risk for bipolar disorder (because they have a parent with the disorder) three types of symptoms were the best predictors of later bipolar disorder: anxiety/depression at the time participants entered the study, unstable mood or irritability both when entering the study and shortly before a bipolar diagnosis, and low-level manic symptoms observed shortly before diagnosis.
The earlier the age at which a parent was diagnosed with a mood disorder, the greater the risk that the offspring would also be diagnosed with bipolar disorder. Youth with all four risk factors (anxiety or depression, mood changes, low-level mania, and a parent who was diagnosed with a mood disorder at an early age) had a 49 percent chance of developing bipolar disorder, compared to a 2 percent chance among those without those risk factors.
Childhood onset of bipolar disorder and long delays until first treatment for depression or mania are both significant predictors of a poor outcome in adulthood compared to adult onsets and shorter delays to treatment. Read more
Stimulants are one of the most common medications prescribed to children and adolescents, typically for attention deficit hyperactivity disorder (ADHD). In children of parents with major depression, bipolar disorder, or schizophrenia, stimulant use may come with a risk of psychotic symptoms. A 2016 study by L.E. MacKenzie and colleagues in the journal Pediatrics reported that among children and youth whose parents had one of these psychiatric illnesses, 62.5% of those who had taken stimulants had current psychotic symptoms, compared to only 27.4% of those who had not taken stimulants. The participants with psychotic symptoms tended to have hallucinations that occurred while they were taking stimulants. Doctors may want to consider whether parents have a history of psychiatric illness when deciding whether to prescribe stimulants to children and adolescents with ADHD. Activation is a common side effect of antidepressants in children who have a parent with bipolar disorder. Young people taking stimulants for ADHD should be monitored for psychotic symptoms, particularly if they have a parent with a history of depression, bipolar disorder, or schizophrenia.
Researcher Juan David Palacio reported at the 2015 meeting of the American Academy of Child and Adolescent Psychiatry that compared to offspring of non-ill parents, children of parents with bipolar I disorder are at high risk for psychiatric disorders, particularly bipolar spectrum disorders and substance use disorders. They were also at risk for symptoms of anxiety disorders and conduct disorder. Palacio’s findings from Colombia mirror those from other studies of familial risk and suggest the importance of vigilance to detect these disorders early and provide appropriate treatment. Our Child Network may help.
In a talk at the 2015 meeting of the International Society for Bipolar Disorders, researcher Eric Youngstrom showed that mothers’ evaluation of their children’s psychiatric symptoms was more valid than both teacher ratings and the children’s own evaluations. Parents were better at detecting irritability, while children were better at assessing their energy levels and the quality of their sleep.
Youngstrom reported that about 2% of children worldwide are diagnosed with bipolar disorder. However, when bipolar disorder not otherwise specified (BP NOS), a diagnosis given when symptoms do not meet the diagnostic criteria for Bipolar I or II, is included in the statistics, rates of bipolar disorder among children in the US reach about 6%.
Youngstrom mentioned that an epidemiological study by Kathleen Merikangas found that among children in the US with a bipolar spectrum diagnosis, only 22% were in treatment, compared to 38% of those with depression and 60% of those with ADHD.
Parents of children (aged 2–12) with mood, anxiety, and behavioral disorders are invited to join the Child Network, our program for tracking weekly symptoms which can then be printed out longitudinally to share with the child’s doctor.
At a symposium at the 2015 meeting of the International Society for Bipolar Disorder, researcher Rudolph Uher discussed FORBOW, his study of families at high risk for mood disorders. Offspring of parents with bipolar disorder and severe depression are at higher risk for a variety of illnesses than offspring of healthy parents.
Uher’s data came from a 2014 meta-analysis by Daniel Rasic and colleagues (including Uher) that was published in the journal Schizophrenia Bulletin. The article described the risks of developing mental illnesses for 3,863 offspring of parents with schizophrenia, bipolar disorder, or major depression compared to offspring of parents without such disorders.
Previous literature had indicated that offspring of parents with severe mental illness had a 1-in-10 likelihood of developing a severe mental illness of their own by adulthood. Rasic and colleagues suggested that the risk may actually be higher—1-in-3 for the risk of developing a psychotic or major mood disorder, and 1-in-2 for the risk of developing any mental disorder. An adult child may end up being diagnosed with a different illness than his or her parents.
At the symposium, Uher focused on families in which a parent had bipolar disorder. These families made up 1,492 of the offspring in the Rasic study. The table at right shows the risk of an illness among the offspring of bipolar parents compared to that risk among offspring of healthy parents, otherwise known as relative risk. (For example, offspring of parents with bipolar disorder are 4.24 times more likely to be diagnosed with bipolar disorder themselves than are offspring of non-bipolar parents.) The table also shows the percentage of offspring of parents with bipolar disorder who have each type of disorder.
Editor’s Note: These data emphasize the importance of vigilance for problems in children who are at increased risk for mental disorders because they have a family history of mental disorders. One way for parents to better track mood and behavioral symptoms is to join our Child Network.
A new longitudinal study of 391 youth at risk for bipolar disorder revealed some predictors of the disorder. The study by Danella M. Hafeman and colleagues was presented at the 2015 meeting of the Society of Biological Psychiatry. The participants were aged 6–18 and each had a parent with bipolar disorder. Over the course of the study, 40 developed an illness on the bipolar spectrum, including 21 who developed bipolar I or II. The participants were assessed for various descriptive characteristics and those who developed bipolar disorder were compared to those who developed major depressive disorder.
The most important predictors of bipolar disorder were parental assessment of internalizing symptoms of anxiety or depression, self-assessment of mood changeability, and self-assessment of hostility. A diagnosis of bipolar disorder not otherwise specified (BP-NOS) was the only predictor of a later diagnosis of bipolar I or II.
Editors Note: These data resemble findings from a 2015 study by David Axelson and colleagues in the American Journal of Psychiatry that used the same cohort of participants. The Axelson study indicated that a categorical diagnosis of a major psychiatric disorder occurred in 74% of the offspring of a bipolar parent compared to about 50% in a control group from the community. Depression, anxiety, attention deficit hyperactivity disorder (ADHD), and oppositional disorders were even more common than bipolar disorder in the at-risk population.
The presence of a major psychiatric diagnosis in about three-quarters of the offspring of a parent with bipolar disorder suggests the importance of early vigilance. One way to track symptoms of depression, anxiety, ADHD, oppositional behavior, and bipolar disorder is to join the Child Network, a secure online platform for rating children’s moods, medications, and side effects. These weekly ratings can be collected longitudinally and printed out to help parents and clinicians assess mood difficulties in their children.
Relatively little attention has been paid to the children of a parent with bipolar disorder, who are at risk not only for the onset of bipolar disorder, but also anxiety, depression, and multiple other disorders. These children deserve a special focus, as on average 74.2% will receive a major (Axis 1) psychiatric diagnosis within seven years.
New research published by David Axelson and colleagues in the American Journal of Psychiatry describes a longitudinal study comparing children who have a parent with bipolar disorder to demographically matched children in the general public. Offspring at high risk for bipolar disorder because they have a parent with the disorder had significantly higher rates of subthreshold mania or hypomania (13.3% versus 1.2%) or what is known as bipolar disorder not otherwise specified (BP-NOS); manic, mixed, or hypomanic episodes (9.2% versus 0.8%); major depressive episodes (32.0% versus 14.9%); and anxiety disorders (39.9% versus 21.8%) than offspring of parents without bipolar disorder. Subthreshold episodes of mania or hypomania (those that resemble but do not meet the full requirements for bipolar disorder in terms of duration) were the best predictor of later manic episodes. This finding was observed prospectively, meaning that patients who were diagnosed with manic episodes during a follow-up assessment were likely to have been diagnosed with a subthreshold manic or hypomanic episode during a previous assessment.
The study included 391 children (aged 6–18) of at least one bipolar parent, and compared these to 248 children of parents without bipolar disorder in the community. The participants took part in follow-up assessments every 2.5 years on average, for a total of about 6.8 years. Each follow-up assessment included retrospective analysis of symptoms that had occurred since the previous assessment.
In addition to having more subthreshold manic or hypomanic episodes; manic, mixed, or hypomanic episodes; and major depressive episodes, the high-risk children also showed more non-mood-related axis 1 disorders, including attention deficit hyperactivity disorder (ADHD), disruptive behavior disorders, and anxiety disorders than the children of parents without bipolar disorder. Axelson suggested that monitoring for these symptoms may help with early identification and treatment.
Children with a bipolar parent were diagnosed with bipolar spectrum disorders at rates of 23% compared to 3.2% in the comparison offspring. Mean age of onset of mania or hypomania in the high-risk offspring was 13.4 years. Of those offspring who had a manic episode, more than half had the episode before age 12, with the earliest occurring at age 8.1.
Compared to previous studies of children of parents with bipolar disorder, this study found that the mean age of onset of manic or hypomanic episodes was younger, possibly because other studies did not include young children. Another new finding was that major depressive episodes were risk factors for mania and hypomania but did not always precede the onset of mania or hypomania in the high-risk offspring.
Parents of children who are at high risk for developing bipolar spectrum disorders should be aware of the common precursors to mania—subthreshold manic or hypomanic symptoms and non-mood disorders—and make sure that clinicians assess for these symptoms and differentiate them from the symptoms of depression or other disorders.
Editor’s Note: In Axelson’s study, 74.2% of the offspring of a bipolar parent suffered a major (Axis I) psychiatric disorder. However, 48.4% of the offspring from the comparison group of community controls also had an Axis 1 psychiatric disorder. These high rates of illness and dysfunction indicate the importance of monitoring a variety of symptom areas and getting appropriate evaluation and treatment in the face of symptoms that are associated with impairment in both high risk children and in the general population.
One way of doing this is for parents to join our new Child Network, a study collecting information about how children at risk for bipolar disorder or with symptoms of bipolar disorder are being treated in the community and how well they are doing. Parents rate their children on a weekly basis for depression, anxiety, ADHD, oppositionality, and mania-like symptoms. Parents will be able to produce a longitudinal chart of their children’s symptoms and response to treatment, which may assist their child’s physician with early detection of illness and with treatment. See here for more information and to access informed consent documents.
Korea, like the US, has a moderate incidence of childhood-onset bipolar disorder among children who are at high risk because they have a parent with bipolar disorder. In a recent study by Young-Sun Cho et al. presented at the 2014 meeting of the International College of Neuropsychopharmacology (CINP), 59 out of 100 children with a parent who had been diagnosed with bipolar disorder met the criteria for a mental disorder themselves.
Mood disorders were most common. Of the 59 children with mental disorders, 22 were diagnosed with bipolar disorder, and 16 were diagnosed with a depressive disorder. Others included four with attention deficit hyperactivity disorder (ADHD), four with an anxiety disorder, two with disruptive behavior disorders, one with a tic disorder, one with an autistic disorder, and one with schizophrenia and an anxiety disorder.
Editor’s Note: In contrast to studies in Germany, Switzerland, the Netherlands, and Canada, where few children are diagnosed with bipolar disorders (even among those who are at high risk because of a family history of bipolar disorder), 22% of high-risk children in Korea were diagnosed with bipolar disorder. This is comparable to or higher than rates at which high-risk children in the US are diagnosed with bipolar disorder. Studies from both the Bipolar Collaborative Network (in which this editor Robert Post is an investigator) and researcher Boris Birmaher et al. found that parents with bipolar disorder often had a variety of other disorders, such as anxiety, alcohol abuse, or substance abuse. These other illnesses also increase the risk of early-onset bipolar disorder in offspring, and this may account for the higher incidence of early-onset bipolar disorder among high-risk children in the US.