It is usually due to genetics or stress.

磨牙通常是由遗传或压力造成的。

youdao

About 50% of a person's chronotype is due to genetics.

大约50%的人的时间类型是由基因决定的。

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And some of us may just be inclined to gain weight while others are not, due to genetics.

有些人可能就是易于发胖而另一部分人不会，这应归于遗传。

youdao

Although the causes of obesity are undoubtedly complex, only a limited number of cases are primarily due to genetics.

FORBES: Obesity: The New 'Just Say No' For 2013

However, the higher rate could also be due to genetics.

BBC: Food additives 'affect sight'

Previous research had shown, for instance, that 29% of the variation in whether or not people invest in stocks depends on their DNA. Studies of professional traders had demonstrated that approximately 25% of individual variation in portfolio risk is due to genetics.

WSJ: Jonah Lehrer on Genetics, Dopamine and Wall Street | Head Case