When it comes to risky sexual behaviour, counselling has surfaced as a surprising way to help persuade young men - but not young women - to abstain from premarital sex.

One key factor, according to a study of 688 sexually active teens aged between 16 and 19 in Singapore, is whom they have sex with.

Many of the young men had sex with prostitutes or casual partners, while an overwhelming majority of the young women had sex with their boyfriends.

Said Associate Professor Wong Mee Lian, the study's principal investigator: "It's easier for the young men to avoid having sex with sex workers or casual partners as they initiate the act. They have more control. But the young women are on the receiving end and it's harder for them to say no to their boyfriends as they see sex as a way to convey love and trust."

The behavioural intervention trial, which was published in Health Education Research, a journal, this month is the first of its kind on sexually active adolescents in a clinic setting in Asia.

The teens were new patients of the Department of Sexually Transmitted Infections Control (DSC) Clinic. About 40 per cent of them tested positive for sexually transmitted infections (STIs).

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LEARNING TO SAY NO Our intervention is not just about giving them knowledge. We stress giving them the skills to, for example, say no. We do not force our message on them but we tailor our messages to what matters to them. ASSOCIATE PROFESSOR WONG MEE LIAN, on how researchers counselled patients in the intervention group to change their behaviour.

Those in one group, known as the intervention group, were counselled to change their behaviour.

Members of another group, the control group, received the routine care by DSC staff. Dr Martin Chio, head of the DSC Clinic, said patients in the control group were assessed on their symptoms and depending on the doctor's assessment, they were given further health advice and counselling.

The study was a follow-up to an earlier one, published in 2009, that identified what makes it likelier for teens here to have premarital sex. (See other story)

There was a spike in sexually transmitted infections (STIs) among teens a decade ago, with 820 people between 10 and 19 years old diagnosed with STIs such as gonorrhoea in 2007. This was more than thrice the 256 diagnosed in 2001.

So Prof Wong, who is from the Saw Swee Hock School of Public Health at the National University of Singapore, and her team wanted to find ways to arrest the trend. Her co-authors are Dr Junice Ng, Adjunct Professor Roy Chan, Dr Martin Chio, Dr Raymond Lim and Professor David Koh.

In their latest study, the median age when these young people lost their virginity was 16, although a few started having sex when they were as young as 10.

The boys had a median of three sexual partners by the time they were polled, while the girls had four.

The intervention group attended three sessions held by the researchers, where they were asked to reflect on their influences and to set goals for themselves, to abstain from sex or stay faithful to one sexual partner, for example.

They were also educated about STIs and taught how to refuse requests for sex, or to get their partners to use a condom, among other things. Said Prof Wong: "Our intervention is not just about giving them knowledge. We stress giving them the skills to, for example, say no. We do not force our message on them but we tailor our messages to what matters to them."

After six months, 41 per cent of the young men in the intervention group had abstained from sex - double the control group's figure.

This approach had no significant impact on the women, although the researchers had some success in getting them to stick to one partner. The young women in the intervention group were 1.3 times more likely than those in the control group to have stuck with one partner, at the follow-up six months later.

Prof Wong acknowledged that it is tough to get some of these young people to abstain from sex, given their life experiences. So another strategy is to get them to use condoms and to have just one sex partner, to reduce their chances of getting or passing on STIs.

She gave the example of one girl who started having sex when she was 11 with a boy from school, and remains sexually active about five years later. The girl's mother is a sex worker. "It's hard for her to abstain as sex has become a norm for her. She feels it's her way to show her love when a boy asks her for it."

Ms Tan Bee Keow, director of the youth service centre at the Singapore Children's Society, noted that being able to stick to one partner for six months was significant, as at-risk youth tend to have very short-lived relationships.

"Their relationship can be as short as one week and they would have had sex in that week," she said. "Some say one month is a long (relationship) already."

Ms Iris Lin, head of youth services at Fei Yue Community Services, said: "For the boys, sex is more about their self-satisfaction. But for girls, it is to satisfy their partner and so it's harder for them to say no. They fear it will jeopardise their relationship or their boyfriends will leave them if they don't have sex."

Prof Wong said her team has shared its findings with the DSC clinic. The clinic's head, Dr Chio, said the DSC has been analysing the study's findings and exploring interventions it could use in counselling its teenage patients.