Washington, Aug 7 (IANS): Online harassment or cyberstalking is more stressful and traumatic than its physical equivalent.

Emotional responses may include high levels of ongoing stress, anxiety, fear, nightmares, shock and disbelief, helplessness, hyper-vigilance, eating and sleeping difficulties, according to a new study.

"Increasingly, stalkers use modern technology to monitor and torment their victims," said Elizabeth Carll, who heads the media division of the American Psychological Association (APA).

"One in four victims report some form of cyberstalking, such as threatening e-mails or instant messaging," she said.

"The impact is more devastating due to the 24/7 nature of online communication, inability to escape to a safe place and global access of the information," she added.

US Justice Department statistics reveal that some 850,000 adults, majority females, are targets of cyberstalking each year, Carll said according to an APA statement.

Forty percent of women have experienced dating violence via social media which includes harassing text messages and disturbing information about them on social media sites.

Researchers examined data collected in 2009 from 1,112 students, ages 12 to 19, including 405 females, from schools in Seoul and the Keonggi area of South Korea.

The students completed a questionnaire about their cyberbullying experiences, self-esteem and how they regulate their emotions.

"The results revealed that cyberbullying makes students socially anxious, lonely, frustrated, sad and helpless," said presenter YeoJu Chung of South Korea's Kyungil University.