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. Last Updated: 07/27/2016

Experts Mull Genetic Trait Behind Suicidal Tendency

LOS ANGELES -- The sad chain of suicides that has plagued the talented Hemingway family for three generations may be due to a genetic trait passed unwittingly through the clan, mental health experts say.

The Los Angeles County coroner's office recently ruled Margaux Hemingway's July 1 death a suicide by massive barbiturate overdose. The former model's suicide is the fifth among four generations of relatives. Her famous grandfather, Ernest Hemingway, killed himself with a shotgun 35 years ago. The novelist's father, brother and sister also committed suicide.

But two or more suicides are not unusual in a family with a history. One in every four people who attempts suicide has a family member who also tried to commit suicide, according to a study of 2,304 Los Angeles residents completed several years ago by the National Institute of Mental Health.

"If you look at spectrum of suicide behavior -- attempts and completions -- the majority of completers have a family history. It's the rule, not the exception, to have a history of suicidal behavior," says Dr. David Brent, a psychiatrist at the Western Psychiatric Institute in Pittsburgh and one of the nation's leading researchers on suicide.

Suicide is the eighth leading cause of death in the United States. Nearly 1 percent of Americans die by their own hand.

In most cases, people who succumb to suicide have an existing mental illness; usually depression or bipolar disorder, an illness that features bouts of depression alternating with manic behavior, Brent says. Some suicide victims also are substance abusers.

But recent studies even indicate there may be a specific gene or genes that increase the risk of suicide in certain families.

Studies have followed twins who were separated at birth or adopted children to tease apart the possible inherited tendencies toward suicide from environmental influences.

"A number of these studies suggest that suicide is associated with a family history but doesn't seem to be explained by psychiatric disorders alone," he says. "There is something else that is familially transmitted."

One researcher investigated an Amish community with high rates of depressive disorders. The study showed that suicides were clustered in particular families, with 73 percent of the suicides occurring in 16 percent of the families in the community, Brent says.

"There were two large pedigrees, both of whom were loaded with depressive illness, but only one pedigree was filled with suicide," Brent says.

What is it about this Amish family -- and others -- that leads its members to opt for suicide?

Despite this well-recognized pattern of family suicides, the answer still isn't clear, Brent says. But the question has ignited a number of research efforts to identify possible mechanisms in the brain that predispose people to suicide.

One line of research has discovered low levels of a metabolite of serotonin, called 5-hydroxyindoleacetic acid, in the brains of people who commit suicide, a characteristic that may be inherited. Serotonin is a neurotransmitter that is involved in the control of impulses, particularly those involving aggression or violence.

People with this deficiency may be 10 times at greater risk of committing suicide, according to the 1995 book "Caring for the Mind," by Dianne Hales and Dr. Robert Hales.

"It's all a little shaky," says Brent of the research. "But many studies have been able to identify that these people are very low in something related to serotonin. This is the strongest single finding in this type of research."

Part of the resounding impact of suicide on families is that relatives fear it runs in the family. Young people, in particular, worry that they will feel an irresistible urge to take their own lives, experts say.

But studies show that imitation probably has limited influence, Brent says. Still, he admits, that concept offers little comfort to families with a history of suicide. Members wonder if they will feel powerless to control the urge to end their lives in moments of despair.

"A lot of times survivors will ask me, 'Am I at increased risk?' The answer is that survivors are at fourfold increased risk. But I tell these people that suicide is still relatively rare. It's still unlikely they will kill themselves. On the other hand, they have the opportunity to be increasingly vigilant about the precursors."

There are other, less potent, factors that impinge on the moment when a suicide occurs. These include an easy means to kill -- guns, a stockpile of drugs -- and the absence of other people to thwart the act.

In Hemingway's case, those little extras may have allowed her to act on an inherited sensitivity. She had the drugs. And she was alone. She even fit the profile.

According to the Hales, unmarried women with a family history of suicide are more likely to attempt suicide than men or married women with similar backgrounds.

When Joan Rivers' husband, Edgar Rosenberg, took his life, she said for other members of the family, suicide then becomes "a viable option."

"After it becomes a reality in your family, it's a definite way out," Rivers was quoted as saying.