Pham Thi Huong (not her real name) from the Mekong Delta Province of Kien Giang decided to take her four-year-old son to a hospital in HCM City after she noticed him blinking all the time, displaying facial twitching and experiencing occasional nausea.

At the hospital, Huong was shocked to hear that her son had been diagnosed with a tic disorder, defined as having uncontrolled sudden, repetitive movements difficult to control.

There are two types of tics – motor and vocal. Motor tics are sudden short movements, such as twitching, grimaces, or squints. A vocal tic might be repetitive sniffling, throat clearing or coughing, clicking of the tongue or humming.

According to Dr. Nguyen Quang Vinh, Head of the Department of Neurology of the HCM City Children’s Hospital 1, gaming, playing with smart phones or watching TV in long hours are among the main cause of tic disorder in children.

"When children play games, use the phone or watch TV too much, the eyes and nerves are always in a state of high concentration leading to stress, not only increasing refactrive errors but also causing the onset of tic disorder, " he told the Bnews online newspaper. Some other factors can also lead to tic disdorder, such as academic stress, or being scolded.

Huong said since her son was two years old, he had been hyperactive and she let him watch videos and play games on mobile phones so that he could sit quietly. Huong’s son is not alone.

On average, about five to seven children are taken to the hospital every day with tic disorder, Vinh says.

Doctor Vinh warned that in the summer, the number of tic cases grows because children are not at school and they use smart phones more often.

A social survey by the Research Centre of Culture, Education and Social Life under the HCMC Ethnology and Anthropology Association in 2014 found that up to 78 per cent of kids under six years old use digital devices.

Conducted in four major cities - HaNoi, Da Nang, HCMC and Can Tho - the survey gathered replies from 1,051 respondents, who are parents of 1,802 kids from three to 12 years old. The survey also found the children were using their devices for an average of 30-60 minutes a day.

Tic syndrome is more common at the ages of four to 10. Although not dangerous, it can lead to social and physical problems, Vinh said. Doctors usually prescribe medication to relieve the nervous system of the child, and in some cases suggest psychological treatment.

According to Vinh, the possibility of tics recurring is high so parents need to limit children’s use of mobile phones and TV watching. Children should go out to exercise and participate in other activities to release energy, he said.