What should you do when you teen starts mixing with a bad crowd? And what if you suspect drugs are involved? Raisingkids.co.uk's child psychologist Dr Pat Spungin helps you find the balance between letting go and over-protecting your teenager.

Raisingkids member's problem
My 14 yr-old has been swimming since he was 9, and has swum in the 'Southern Counties'. He suffers from asthma and eczema, and last year became ill with glandular fever for 9 months. Now he's taken up with a bad crowd, and has started smoking, hanging around shops and fighting. He even wants to give up swimming to make more time for his new friends. I've heard rumours of these boys stealing and taking drugs, and recently I found cigarette papers in my son's possessions, an indication he's smoking cannabis. My husband says I should have more faith in him and to let him learn by his own mistakes but I'm extremely concerned for his future health. What do I do?

Dr Spungin's advice
I can appreciate your worries - your son seems to have fallen in with bad company and I think the first thing both you and his father should do is talk to him about it. Find a place where you won't be distracted and have a heart-to-heart with him. For guidance on how to reach an understanding with your son and avoid conflict, see our Parenting Skills section.

Without lecturing or nagging, explain you're concerned about the way things are going. He won't want to upset you, but he won't like it if you criticise his friends, so don't make it easy for him to storm off. Keep the conversation low-key so he has no excuse not to listen or talk to you. Friends are very important to teenagers and influence the way they behave. Peer group influence is very strong at this age - our Discussions have lots of support and advice from other parents experiencing similar problems.

Many teenagers smoke cannabis believing it's less harmful - or no more harmful - than cigarettes. It does, however, have side effects and will undoubtedly affect his ability to do sports and school work. We get many queries of this type about teenagers - it's a difficult time for parents. The most important thing you can do is keep talking.

• More Answers From Dr Pat Spungin
• Parenting Skills
• 'My Teen Is Smoking Pot' - Can You Help?
• Discussion: My Teenage Son