A new study published in the recent issue of Science magazine found out that a person's risk of having depression or being addicted to nicotine may have been inherited from Neanderthal DNA.

The group of researchers studied 28,000 electronic health records of Americans with European ancestry and used a new method to scan for Neanderthal gene variants that are linked to depression and other disorders like skin lesions and blood clots.

"We discovered and replicated associations of Neanderthal alleles with neurological, psychiatric, immunological, and dermatological phenotypes. Neanderthal alleles together explained a significant fraction of the variation in risk for depression and skin lesions resulting from sun exposure and individual Neanderthal alleles were significantly associated with specific human phenotypes, including hypercoagulation and tobacco use," the paper stated.

John A. Capra, an evolutionary geneticist at Vanderbilt University and is helped by 20 other individuals, is the paper's senior author. Sriram Sankararaman from UCLA told the Associated Press that he is very excited with the new research, as he also studied Neanderthal DNA back in 2014.  

Link with Depression and Nicotine Addiction

The study found a number of Neanderthal DNA variants that were linked with the brain functions likely increasing the risk of depression and nicotine addiction, per phys.org. "The brain is incredibly complex, so it's reasonable to expect that introducing changes from a different evolutionary path might have negative consequences," co-author Corinne Simonti said.

Anne Gibbons of ScienceMag.Org noted that depression was possibly triggered in Neanderthals when their circadian rhythms were disturbed. However, Sankararaman said that it is not yet clear how these discovered gene variants affects Neandertals directly, which would mean that they were not always depressed.

As for the nicotine addiction link, a new Neanderthal allele was found to increase the risk of using tobacco. It is the second Neanderthal allele discovered by researchers that is linked with addiction to nicotine.

Link with Skin Lesions and Blood Clotting

According to phys.org, the study has also proven existing hypotheses from past studies including those about keratinocytes. Capra and his colleagues have discovered that Neanderthal DNA variants can cause an abnormal number of keratinocytes leading to skin lesions called keratosis induced by prolonged exposure to sunlight.

On the other hand, another Neanderthal variant is found to increase blood coagulation that is responsible for clotting. It is believed that it helped Neanderthals prevent different types of harmful microorganisms to enter their body as wounds heal faster. However, the variant is also found to be responsible for hypercoagulation in modern people as it increases the risk of disorders like pulmonary embolism, complications in pregnancy and stroke.