suicide

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There’s something extremely tragic about a suicide, perhaps even more so than deaths caused by other non-self-inflicting causes. Some diseases have an inevitable outcome but is this the case for most suicides too? That’s what hurts the most for the loved ones left behind — this uncertainty; that there was something they could have done to avert the tragedy. People kill themselves for all sorts of reasons. Sometimes, life can be so overwhelming that the only seemingly practical solution is to end it all. It might a tough childhood, substance abuse, a broken marriage — but there’s a genetic makeup to it, too.

People who complete suicide or who have suicidal thoughts or behavior are more likely to have a family history of suicide. While some family members might feel ‘inspired’ by their suicidal siblings and relatives, it seems there’s some actual genetically driven behavior. Studies on twins suggest monozygotic twin pairs have a significantly greater incidence of both completed and attempted suicide than dizygotic twin pairs. Suicide is also most common among biological relatives of adopted suicides than among biological relatives of adopted controls. A 2003 study involving 21,168 Danes over a 17-year period found that the suicide mortality in the first-degree relatives of suicide victims is about 3.5 times that in the first-degree relatives of live controls who are matched for age, sex and date of suicide.

The overall findings from clinical, twin, adoption and laboratory molecular genetic studies suggest that there is a genetic susceptibility to suicidal behavior in people with severe stress or mental disorders. Now, Japanese researchers think they have uncovered some of the pathological features that may lead to suicide at a cellular level.

The team investigated how the chromosomes and mitochondria differed in people who committed suicide. They collected blood samples from 508 suicides and 538 healthy, living controls but also the brains from 20 suicides and 25 controls. They then proceeded to measure telomere length and the mitochondrial DNA copy number (mtDNAcn) using a method called quantitative polymerase chain reaction (qPCR).

The conclusion was that people who had committed suicides had significantly shorter telomeres than healthy controls. This pattern was visible in young people (aged 34 and younger) and middle-aged women (35-59) but no longer apparent for elderly people, likely because telomeres shorten as we age. In white blood cells, the length of telomeres ranges from 8,000 base pairs in newborns to 3,000 base pairs in adults and as low as 1,500 in elderly people.

They also found mtDNAcn was significantly higher in those who committed suicide. Oddly, this pattern held true for elderly people but not for young or middle-aged participants. Young people have higher levels of mtDNAcn.

When the brain samples alone were considered,  both telomere length and mtDNAcn were lower among people who committed suicide.

The results seem a bit contradictory but they at least suggest a trend where biology is linked to suicidal events. Further studies might be able to shed light in broader detail. If they can confirm the findings, telomere length could serve as a biomarker for the risk of suicide.

“In conclusion, we report the first association of aberrant telomeres and mtDNAcn with suicide completion. Our results raise the possibility that further research into telomere shortening and mtDNA dysfunction may elucidate the molecular underpinnings of suicide-related pathophysiology,” the authors wrote.

Journal Reference: Ikuo Otsuka, et al. “Aberrant telomere length and mitochondrial DNA copy number in suicide completers.” Scientific Reports 7, Article number: 3176. Published: 9-June-2017. doi:10.1038/s41598-017-03599-8

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