Teenagers can seem worlds away from those darling little children we knew just a few years before.

All of a sudden you feel more and more isolated from your kids. Doors are slammed and grunting replaces conversation until the wailing starts when they don't get their way.

We've asked Professor Ian Hickie of Headspace, the government-funded National Youth Mental Health Foundation, and adolescent specialist Professor David Bennett to answer the questions that plague many parents.

My drugs dilemma:

My son gets drunk and smokes marijuana every weekend. What should I do?
Jenny, via email.

'Firstly, don't appear shocked or furious - this puts their behaviour on a pedestal,' says Professor David Bennett, specialist in adolescent medicine at The Children's Hospital, Westmead.

'Don't yell or use negative language. They'll associate it with you putting them down and this erodes self-esteem and can lead to more destructive behaviour. When you've calmed down, discuss what's going on. Point out realities, such as car accidents being the number one killer of young people and marijuana increasing schizophrenia in people who smoke in their teens.'

If your child still refuses to listen, Professor Bennett suggests getting outside help. 'Health professionals aren't 'parents', and they tend to have authority and may have already gained your child's trust,' he says.

Also, be firm about your expectations and discuss the punishments for breaking them.

'If your child continues to behave in a dangerous way, tell them they're grounded - and stick to it,' Professor Bennett says. 'Curtailing pocket money can also have the desired effect.'

Other tips include being a good role model and never encouraging kids to drink or smoke marijuana with you because you think it's safer for them to do it at home.

My child has started to smoke cigarettes. How can I make her stop and not look like a hypocrite because I smoke too?'
Simon, Gold Coast, Q.

'Do as I say, not do as I do' doesn't cut it with kids today,' says Professor Ian Hickie, of the government's new $54 million Headspace program. 'It's not about preaching, it's about facts. If you don't give up, there's a greater chance your child will continue to smoke.'

But what if you've already tried to quit smoking and have been unsuccessful?

'Not everyone finds it hard to quit smoking,' Professor Hickie says. 'The people who can't give up easily, or quit and start again, often have an underlying and untreated depression - the desire to smoke is often just another symptom of this depression. We've had enormous success with people giving up once the underlying issue is treated with counselling and, when necessary, medication - often for just six to 12 months.'

Make sure you also highlight some of the unpleasant side effects of smoking, such as smelly fingers and breath, erectile dysfunction and even gangrene, heart disease and cancer.

Home Run

How do I get my teen to come home on time?
Michael, via email.

'Be flexible but be sure you know where they'll be and with whom,' Professor Bennett says. 'Monitoring and supervision can protect them from risky behaviour.

'But teens love autonomy. Respect this and ask: 'What time do you think is reasonable to get home?' Then you can negotiate from there.'

How do I know if my child is depressed?
Nigel, St Kilda, V.

Signs of depression, mental health problems or substance abuse include:

• Moodiness or anxiety
• Sleep disturbances
• Tearfulness
• Eating too little or too much
• Dark, suicidal or violent thoughts (may manifest in drawings, letters or aggressive music)
• Irritability
• Loss of interest in things they used to love
• Tremors and glazed eyes
• Heavy risk-taking.

Professor Hickie says one in four Aussie teens and young adults have a mental health problem, such as drug and alcohol abuse, an eating disorder or depression.

'If your teenager's habits and moods are becoming worse and you're feeling more isolated from them, there's a high chance there's an underlying mental health issue,' he says. 'You need to act early.'

The good news is that the Headspace program aims to provide troubled young people with a holistic approach to mental health. There will be doctors, psychiatrists, psychologists and social workers - often under one roof - in 10 centres across Australia. And there are more centres to come.

'A lot of the time parents feel they can't afford these visits, so we're hoping much of the services will be free or at a very low cost,' Professor Hickie says.

'My Pledge' - For Parents:

• We agree to pick you up at any time, day or night, from anywhere, for any reason, to give you a safe ride home. We will also give your friends a lift home.
• We agree to discuss any matters arising from our pledge in a calm and rational manner.

'My Pledge' - For Teenagers:

• I agree not to drive while drunk, taking drugs or when tired.
• I agree to call you for help, regardless of time, place or reason.
• I agree not to get a lift from anyone I suspect is drunk, tired, an inadequate driver or someone I don't know or trust.
  

Give and Take
With a bit of compromise, you can usually turn things around with your troublesome teen. But if things have gone too far, check out Headspace, a new service for young people aged
12 to 25. For more information and to find services in your state, visit www.headspace.org.au

What is the best way you have found to deal with teens' difficult beahviour? Discuss with other New Idea readers below