I am very worried about my preteen son. As a young woman, I struggled with addiction, but I have been clean for 24 years and am now a mother. I have heard that my siblings have told their children about my addiction; I’d wanted to protect my son from this, but my sister is spreading rumours and untruths, and I am afraid to have her or her family near mine.

Soon, my son may hear about this, and I don’t know how to handle the situation. How do I teach him about not taking drugs if I took them? And what will he think of me? It’s devastating.

You’re being really hard on yourself, and defining yourself by your past addiction; that’s not who you are now. Like a lot of parents, you think that by talking to your child about something contentious (sex and drugs are the usual ones), it’s a prescription for them to do those things. Actually, it informs, rather than dictates, and children then know – if you can talk about such subjects dispassionately and factually – that if anything goes wrong, they can come and talk to you about it.

I’m not sure why your family are spreading rumours about something they have no ownership over. But even if you didn’t have the threat of them telling your son, I think this is something you should broach with him. You certainly need to pre-empt any revelations from them. I know you’re scared, but try to examine what it is you are frightened of. Him judging you? Unlikely, especially at his age.

I talked to Rebecca Harris, a family psychotherapist who specialises in addiction; she felt there was a lot of shame in your letter. “You’ve been clean for 24 years, but you don’t seem to focus on what you have managed to achieve, or give yourself credit for it,” she said. “It’s lovely that you want to protect him but secrets often come out, and children do pick things up. It’s far better that you give your narrative and tell him how it really was, rather than him hearing it from others.”

Also remember that, if children pick up half-truths, they often fill the gaps with things that are far worse. Imagination can be more vivid than reality. If he does find out from someone else, he will realise you’ve kept it from him, and that could cause further issues between you.

I asked Harris how can you teach your son not to do drugs when you did, because it is a hard one. “Think about how many people who work with drugs and with addicts have been addicts themselves,” she said. “They are much better placed to work in that world. To be able to say, ‘Yes, I did this, yes, I regret it. Here are the reasons I did it, here’s what I discovered. And here’s why it wasn’t OK and why I would prefer you didn’t do this.’ I think that’s really powerful.”

How to bring it up? Harris stressed normalising it, which I appreciate sounds counterintuitive; but be calm and factual, don’t turn it into a big drama. Pick your time and place, maybe when out for a walk (side by side is better than face to face, which can seem intimidating and intense), not when your son is tired or hungry; when he’s in a decent mood. Then you may want to start with something such as, “Have you learned about drugs in school? I’ve got a bit of experience of that of my own.” And go from there.

Harris wondered if you had made your own peace with what happened? Is there someone you could talk this through with first?

Tell your son he can ask questions if he wants to; this is useful if he then hears things from the family, and will teach him critical thinking skills and about how mistruths can spread. Remember it’s OK to say, “I’m not sure” or, “I don’t know” if your son asks something you can’t answer. Say you’ll think about it (this shows thoughtfulness: never a bad thing) and get back to him. Lastly, once you start, there may be a temptation to overshare. Always think, “Is this about me or him?” Some ex-addicts aim to heal through their children’s forgiveness. But that’s not needed here.

• Every week Annalisa Barbieri addresses a family-related problem sent in by a reader. If you would like advice from Annalisa on a family matter, please send your problem to ask.annalisa@theguardian.com. Annalisa regrets she cannot enter into personal correspondence. Submissions are subject to our terms and conditions: see gu.com/letters-terms.

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