"Do you know why teenagers get such a bad name," asked a friend recently. "It's because their parents are going through mid-life crises!" His daughter is only ten and I guess he was explaining away any potential misbehaviour on her part, even if it was going to make him sound bad, but I thought it was a very perceptive statement.

If children are products of their upbringing and conditioning, it follows that watching their parents come apart is going to have an unpleasant effect on their own behaviour. If you've got a fractious teenager in the home or have occasion to watch the parents of one, you'll realise how much truth there is in the statement.

Look at forty-something parents. In most cases they are not all there. Battling their own demons, at best they make distracted custodians. At their worst they probably need to be certified. This is the time when the mother, if she's been relegated the primary child-rearing task, decides enough is enough. She needs a life of her own, one that doesn't revolve around packing lunchboxes and picking up after untidy kids. So she decides to go back to school or get a job. Hit by the sudden urge to 'find' herself, she joins yoga classes, participates in group chanting, and decides the family is going to eat organic.

The bewildered teenager, looking for his poor put upon mother, discovers she isn't to be found. She's out ‘sharing' with other angst-ridden mothers, and on her way home she will pick up some foul tasting food that she thinks is good for her child's brain. "That fatty junk food will kill you," she pronounces, little realising she's planting the seeds of some murderous behaviour in a teenager who's fast reaching the end of his already frayed tether.

He wants to be heard but his mother is immersed in Tibetan chants and the smell of the incense sticks is driving him crazy. He wants to be noticed but mom has that funny glazed look in her eyes because she's had an awful day at work. He wants to retire to his room to listen to some deafening music but that's when mom will emerge from her stupor and spout some psychological claptrap about family time.

So he drags himself sulkily to the family room, where his kid sister is watching the drama with unholy glee, oblivious to the fact that in a few years that could be her. So where is dad? Working late at the office in a feverish bid to stay ahead of the corporate race? Out with the boys getting boisterous or lecherous in some seedy place where their wives can't find them? Slouched over the laptop, engaged in unspeakable things in chat rooms? Yeah, he wonders with disgust, how are we going to have family time when a major participant is missing and mom is too tired or fed up to care?

Can you blame teenagers for going off the rails when their parents are doing such a good imitation of runaway trains themselves? With mid-life comes the realisation of time running out and suddenly normally sane individuals are plagued by all sorts of insecurities. Who am I? Where am I going? How did I get here? Oh my gosh, I haven't yet made a fool of myself over that pretty young thing in Marketing!

When you occasionally emerge from the fugue you discover your child isn't the amenable, adorable little tyke you remember but has metamorphosed into a recalcitrant, disobedient, bad-tempered, moody teenager that you just can't recognise. Take a good hard look at yourself before you start complaining about him.

For all that my friend has made this wise and startling discovery about the cause of teen misbehaviour, I'm hoping he remembers not to lose his cool when his daughter rolls her eyes at his own cranky behaviour in a few years. "I think my son will be luckier," he muses. "By the time he's a teenager I'll be fifty and probably past it!"