Under the cover of darkness, negative thoughts have a way of drifting through your mind, and as you lie awake, staring at the ceiling, you might start craving guilty pleasures, like a cigarette or a carb-heavy meal.

Plenty of evidence suggests the human mind functions differently if it is awake at nighttime.

Their hypothesis, called 'Mind After Midnight', suggests the human body and the human mind follow a natural 24-hour cycle of activity that influences our emotions and behavior.

Humans are much more effective at hunting and gathering in the daylight, and while nighttime is great for rest, humans were once at greater risk of becoming the hunted.

"There are millions of people who are awake in the middle of the night, and there's fairly good evidence that their brain is not functioning as well as it does during the day," says neurologist Elizabeth Klerman from Harvard University.

"Suicide, previously inconceivable, emerges as an escape from loneliness and pain, and before the costs of suicide are considered the student has acquired the means and is prepared to act at a time when no one is awake to stop them," the authors of the 'Mind After Midnight' hypothesis explain.