Sleep experts warned that having smartphones and tablets in bed robs teenagers of a good night's sleep. According to Dr. Michael Hlavac, a sleep psychologist and Christchurch Hospital director, mobile phones and other tablet formats like iPads should be left outside the bedroom when it is time to sleep.

Hlavac cited the latest American study from Washington and Lee University that too much texting can lead to sleep deprivation. The study was conducted by Karla Murdock, a psychology professor who analyzed the sleep and texting patterns of first-year university students. It found that students who lacked sleep had the most number of daily text messages.

Among the responses of the 83 students, many felt pressured to immediately reply to texts without paying attention to the time of day. Many students also have the tendency to sleep with their mobile phones beside them. They always wake up when they receive text messages.

Murdock asked the students to estimate the total number of text messages they send and receive. She used the Pittsburgh sleep quality index to evaluate the students' quality of sleep. The sleep index is a commonly used to measure various sleeping patterns, including sleep duration, night time disturbances and daytime sleepiness.

Hlavac said texting before sleeping is one of the activities that could interrupt a person's "sleep hygiene" and interfere with sleep time. Other activities, like watching television while on the bed, playing games on iPads and computers, also affect sleep patterns.

The study supported previous evidence showing a direct link between smartphone or mobile phone use and sleep deprivation in teenagers and young adults.

It also suggested that text messaging is not an appropriate mode of communication when trying to deal with interpersonal stress in relationships. Murdock stressed that abbreviated language used in texting can be misinterpreted by the receiver as the inability to discuss sensitive matters. She added texting heavily can cause several misunderstandings in dealing with stress, which later lead to conflicts.