For parents, I offer nine guidelines and one golden rule on talking with 14- to 18-year-olds about pornography. These are:

1 Be realistic, so you don’t overreact. Assume your teen has already been exposed to online porn, or knows someone who has.

2 Don’t underestimate their need for confirmation from you that this sort of behaviour in online porn is unacceptable. They behave as if they have it all sorted. But, really, teens still want your guidance. They also want concrete reasons why the behaviours they see in online porn are unacceptable. Ask, for example, “What if this was your sister or brother?” Or, “I’ve always thought that whatever you do during love making and sex play shows a desire to give pleasure to someone you love and to let them know you respect them. Do you think porn acts do that?”

3 Don’t expect them to bring up the subject because they won’t. Most teens feel embarrassed to raise tricky subjects with their parents. Instead, what you want to do is to make it relatively easy to talk through a sensitive topic, and it not make them feel confronted or defensive. Most times you’ll probably have to introduce the topic yourself.

4 Do this in the most non-confrontational circumstances. It’s easier to say difficult things when you’re sharing an activity, because your teen can appear to focus on the activity itself while they’re talking rather than have to look directly at you. Direct eye contact can feel confrontational. For example, talking while sharing a meal is good, or when driving them to and from activities or friends’ homes.

5 Raise the subject obliquely. Asking “have you ever watched porn” will not work, I promise you! Something like this is better: “I just read a survey in the Guardian about schoolchildren and pornography that really surprised me. Do you know anyone who’s watched pornography?” That way, they don’t feel they are the target of this discussion.

6 Once you get going, prioritise listening. Listen more than you talk: allow comfortable silences, and don’t moralise or issue directives. If you do answer, respond with a question as often as you can, such as, “How did that make you feel?” That way, they are more likely to conclude you are taking in and absorbing – rather than judging – what they’re saying.

7 Reassure them that you’ll always listen whenever they want to talk about this topic. It may mean answering the knock by a distressed teen on your bedroom door in the middle of the night, or responding to a call to pick them up from a party in the early hours when things are going wrong. Doing these things shows you value them, and that will help them feel safe and hugely boost their self-esteem.

8 Don’t feel you’re neglecting your responsibilities if they don’t feel comfortable talking to you about this topic – and instead ask if you can help them find someone else to talk to. Help them make an appointment with, say, a doctor in your local surgery. Or you might suggest they talk to an older sibling or aunt or uncle, even a friend’s parent if that seems appropriate. Or you could help them find a professional service or a therapist if that’s what they think would work best.

9 Ask your school to offer parents’ evenings with a professional lead (perhaps a GP or psychologist) present to answer questions about managing exposure to online pornography.

10 The golden rule. Finally, for this and for all the issues you will face when raising children, be the sort of person you hope they will be. The respect and kindness you show to others, the considered and calm way you approach dilemmas and interpersonal issues, these behaviours will influence them far more profoundly than any blocks you try to install on their phones, or even anything you say to them.

Dr Linda Blair is a clinical psychologist