Mental illness runs in families. That’s the underlying theme of the new horror movie “Hereditary,” which premiered at Sundance and opened in theaters June 8. While some aspects of the movie are imaginary or unbelievable, University of Georgia psychology professor Keith Campbell agrees with the story’s underlying premise. “In general, there are significant hereditary factors for mental conditions of all kinds,” he says.
Written and directed by Ari Aster, the R-rated movie follows Annie Leigh (Toni Collette), who is dealing with the recent death of her estranged mother, Ellen. Ellen suffered from dissociative identity disorder (formerly known as multiple personality disorder) and wreaked havoc on her family. Annie’s brother suffered from schizophrenia and killed himself when he was a teenager. Annie is anxious to move forward with her life and put the past and its terrors behind her but is finding this impossible, especially when it becomes clear that her children are suffering from mental disorders and exhibiting disturbing behavior.
Campbell says behavior that looks like adult pathology is pretty common in kids. “My 10-year-old doesn’t regulate her eating and will ingest tons of sugar, for example. She sometimes gets angry and can’t control it. Occasionally she dances with her underwear on. If you did that at age 30, people would think you had some issues.”
In “Hereditary,” however, the little girl’s pathology reaches a much more severe level, as witnessed when she snips off the head of a dead pigeon with scissors.
The film asks important questions: Is mental illness inherited? Can you sidestep the freight train of mental disease coming through your genes? Or are we destined to relive some version of the lives of our family members?
The answer, as you might imagine, isn’t clear cut.
Genetics + environment
Campbell says, “It’s a little hard to quantify, because when we talk about heredity it means I can predict your mental disorder from knowing the mental disorders of your parents and your family. We usually think heredity involves genetics, but there could be other mechanisms involved. Also, genetics always interact with the environment—beginning in utero—and are expressed differently in different people. Inheritance matters, but how it matters is a bit more complicated.”
Typically, when people are talking about heredity they are talking about genetics, said Campbell, adding that most mental diseases are about half heritable. “This means that heritability is about half predicted by family in some way. A lot of mental disorders—such as depression and anxiety—may be in the family but may not come out the same way in everyone. It’s not clean.”
Add external stressors to the mix
Campbell said determining how mental illness will present in a family member is similar to looking at a family history of heart disease. “It could manifest as stroke or as high blood pressure, and your environment—meaning diet, exercise and stress in this case—can play a big role.”
A psychological theory called stress diathesis posits that a disorder is the result of inheritance and external stressors. Campbell explained, “You could have twins, for example, and given different stressors, they turn out differently. Or say you’ve got a kid with a family history of mental illness, such as schizophrenia, bipolar disease and major depression. If you take that kid and expose him to early trauma, such as a death in the family or a crime, the chances he will develop a disorder might increase.”
Difficult to predict
It’s a little harder with mental illness to determine inheritability. “We’re more comfortable with the inheritability of heart disease, weight or cancer,” said Campbell. “But with mental disorders, we don’t have the histories we do with other illnesses because they didn’t have the models we do now for mental illness.”
He added that certain mental disorders such as schizophrenia may be heritable, but also very rare. “Direct relatives are more likely to get schizophrenia than the general population,” he explained, “but it’s still not incredibly common.
Despite advances in the detection and treatment of mental disorders, there will most likely never be a simple genetic test for these illnesses. “There is no schizophrenia gene; there’s no depression gene,” Campbell said. “These disorders are caused by huge numbers of genes and we don’t even understand them exactly.”
The upside of mental illness
Mental illness in lower doses can be helpful, said Campbell. While that may sound odd, he is referring to a 2013 study from Sweden, which revealed that artists and scientists were more common in families where bipolar disorder and schizophrenia is present, compared to the population at large. A nationally recognized expert on narcissism, society and generational change, Campbell added, “A little bit of narcissism doesn’t hurt either.”