Scrolling through social media or watching an online video before you sleep are activities that could lead to depression or anxiety.
That's according to researchers at Seoul-based Sungshin Women's University, who conducted a study on the effects of "bedtime procrastination."
The use of smartphones was seen as one of the biggest reasons for delaying sleep.
A survey on 106 people in their 20s and 30s showed those who put off their bedtime used their smartphones almost five times longer than the average person.
They also tended to use their devices for an hour longer every day.
The research team says these pre-bedtime distractions could impact your health and mental well-being, increasing your chance of becoming depressed by 25 percent, and developing anxiety by 14 percent.
Also, activities that delay your sleep increase the risk of insomnia by 41 percent.
And that risk is even higher at 82 percent for those who use their smartphones before they sleep.
To reduce the chance of developing such long-term mental health complications, the research team stresses the importance of keeping a regular bedtime.
The study was published in the November edition of U.S.-based journal SLEEP.
Oh Soo-young, Arirang News.