A high quantity of phone calls and messages in general was perceived to lead to difficulties relaxing, and therefore to too little sleep or decreased quality of sleep. A high number of messages that had not been replied to could also lead to overload and feelings of guilt. Long phone calls before bedtime could influence sleep negatively, because of headaches or tension. However, the most obvious aspect connecting mobile phone use with sleep disturbances was being awakened at night by phone calls or messages. This meant waking up, checking the phone, and most likely answering or replying to a message. Even with the sound switched off, one could be woken by the sound of a vibrating phone or even by a blinking light. Some felt obliged to check the phone if they woke up at night Other factors that were seen as possible contributors to sleep disturbance were communications with disturbing content, the thoughts provoked by a call or SMS, electromagnetic radiation, and worry about such radiation.(Avvannavar SM et
al.2008, P.82).
In the study to find the association between problematic cellular phone use and risky behaviors and low self-esteem among Taiwanese adolescents. The problematic CPU was associated with insomnia in all groups of adolescents. Meanwhile, problematic CPU was associated with short nocturnal sleep duration in all groups of adolescents except for in girls 15 years or older. With a characteristic of being without predefined stopping points, intensive CPU may lead directly to a reduction in total sleep time by
substituting for it. It may also be the contents of CPU that provokes sleep problems. Late and exciting CPU can cause high arousal and alertness in the brain, thus interfering with the calming effects that are necessary for sleep and delaying the onset of sleep
(Sinha K 2007).