For better or for worse, our body clock dictates our sleep patterns.

How do you feel about your alarm clock? Is it the despised, sleep-destroying herald of that hateful time of day, morning? Or, by the time it starts its beeping, are you already out of bed, going energetically about your gung-ho, sunrise-filled life?

To put the question more concisely: Why is morning a balm to some and a bane to others?

Well, it all depends on your built-in body clock.

Nestled deep in the folds of your brain is a primeval timepiece, an internal clock that ticks out your body’s personal circadian rhythm – a 24-hour cycle that, regardless of morning alarms and evening appointments, your body is naturally inclined to follow.

Your circadian rhythm dictates a great number of things. It’s what guides your body’s desire for sleep – or the opposite of sleep. It’s what makes you want food or drink at certain times. It’s even responsible, to an extent, for moodiness and emotional ups and downs, as well as your metabolic rate.

But here’s the thing: circadian rhythms vary from person to person – a fact that causes a large chunk of the population both to hate alarm clocks and to suffer from health complications.

This portion, which makes up about 30 percent of the population, consists of “night owls,” people whose circadian rhythm inclines them to seek slumber late at night and to rise late in the morning.

Distressingly for these nocturnal folks, society is morning-oriented. School and work typically begin in the morning and last through the afternoon, right when the body clocks of night owls say they should be asleep, or at least still sleepy.

Being out of sync with society’s schedule puts night owls in a tough position: they must get up early even though they fall asleep late. Thus, they’re often sleep-deprived, which makes it likelier that they’ll suffer from a range of illnesses, including diabetes, depression and cancer.