Ash Moran says: 'The best thing about being a teenager is that life is easy. You've got no worries. The worst thing is not having freedom'

‘In my day exams were harder.’ ‘As long as you’re living under my roof.’ Parents, take note: these are the phrases every teenager dreads. Charlotte Philby discovers what really motivates this tricky species...

"The problem with being a teenager is that nothing is ever solid." For a 15-year-old, Ellie Wilson is unusually self-aware; she is also, in her own words "a pain in the arse". "The thing about me and my friends," Wilson shrugs, "is that one minute we're up and then we're down; one minute I want to shout the house down, the next I feel so happy that I just want to hug everyone in the room at once. You know?"

It is, she admits, all a little bit exhausting. On this point, she and her mum are in a rare state of agreement.

The turbulent process of coming of age is one that for generations has left scientists – and parents – quite baffled. Ever since the 1950s, when teenage-dom was finally widely recognised as a bona fide developmental stage, the fundamental point of adolescence has remained a riddle. Tantrums, paralysing inertia, terminal love sickness… Why, when almost every other species seems to manage the transition from infancy to adulthood with relative ease, do we seem to find it so hard?

First we blamed hormones. Then, in the late Nineties, while a generation of young things stumbled their way through their own wilderness years with Karl Kani jeans, The Prodigy and – if you were posh – electronic pagers, scientists at the National Institute of Health (NIH) were making a breakthrough.

Using new scanning systems to monitor brain activity in young people, they found that rather than being fully formed by the end of childhood as once thought, the human mind actually undergoes a massive restructuring during the 12th to 25th years, with the frontal cortex thickening just before puberty and slowly shrinking back to normal size.

Between childhood and adulthood, proved the NIH's study 'The Teen Brain: Still Under Construction', critical physical changes are taking place. These result in impulsiveness, excessive risk-taking, uncontrollable mood swings; all behaviours parents might have thought were designed solely to cause them maximum grief, but which are in fact vital processes in the brain's development.

This may go some way to explain why some of f the more irksome common teenage traits, such as self-doubt and anxiety, often last way beyond the allotted teen years into what psychologist Dr Terri Apter, author of The Myth of Maturity: What Teenagers Need from Parents to Become Adults, defines as the 'thresholder' period, from 18 to 24.

The truth remains, that while science might offer a rational explanation as to why so many teens make irrational decisions (and these are not without potentially hazardous consequences – as the study points out, mortality rates jump between early and late adolescence), it doesn't make everyday communication with teenagers any easier.

Which is where the Surrey-based Megan Lovegrove and Louise Bedwell step in. Earlier this year, the 17-year-old schoolfriends produced Teenagers Explained: A Manual for Parents by Teenagers, a book that was designed to help befuddled adults unpick the peculiar tapestry that is adolescence. f Because, as Lovegrove points out, "there are things we talk about that adults just don't understand".

"Things have changed a lot," Lovegrove adds. "Sometimes I say, 'I'm not skinny enough' and my mum will say 'Don't be stupid', and she just doesn't seem to get the pressures we're under." In order to help adults re-enter the teenage psyche, Lovegrove and Bedwell contacted a selection of young people across the country. While the answers were all different, there were common threads – "For example, everyone said they hated being patronised". Among the most annoying parental expressions, they have identified the following repeat offenders: "In my day exams were harder", "It's not the end of the world", and that old favourite, "As long as you're living under my roof…".

"We're still worrying about bullying, about people thinking that we're weird or different, and about not fitting in," Lovegrove adds. But according to f 15-year-old Wilson, who attends a girls' state school in north London, the stakes are now higher: "On my first day at secondary school a helicopter landed in our playground because a sixth former had pushed one of the teachers out of a window. There are three cat-fights in the playground every day. Boys are all muscle, but girls fight with words and words hurt the most." Plus, she says, with Facebook and instant messaging, there are infinite more ways to express them.

"Try to let us make our own mistakes," pleads Lovegrove. "If we don't get to make our own mistakes when we're young then, at some point, as soon as you're not around, we're just going to explode." The key to being a good parent, she insists, is knowing when to butt in and when to back off: "It's OK to be concerned and to ask questions but please don't question us on everything. Do try to talk to us and make an effort to get to know us, but also understand that there are some things we don't want to talk to you about."

'I'll text my mum because I respect her'

Ash Moran, 18, Dorset

I live in the middle of nowhere, so going to college in Salisbury was a big thing. My old best friend down the road is doing hairdressing in Shaftesbury now. She's stayed in her area and she's not going to go to uni; I can imagine her in 50 years still living in Shaftesbury with her family. I'm going to be living somewhere really random.

When I turned 18 I went out every night for two weeks, but then it got a bit boring. I spend most of the time with my boyfriend – we've been together four months. Every Wednesday, Harry and I go to a pub quiz. He drives so it's quite handy.

When I went to college I wanted to be a hairdresser. I did a course in art and design; now I want to try photography. If that fails I want to work with children. But only when I'm older, like when I'm 40-odd.

The best thing about being a teenager is that life is easy. You've got no worries. You don't need to worry about money because you've got your parents. You're just at school, all you do is just hang out with your mates really. The worst thing is not having freedom because you're stuck at home and you can't really go places. My mum's a single mum – at first if I went to a party she wanted the house phone number, I was like, 'That's ridiculous'. Slowly she's started to trust me more and more, and now she's really relaxed and I'll text her because I respect her. When I have kids I would do it the same way she's done it. I might even ring her for advice.

'Adults: just calm down and stop stressing'

Fern Hardy, 14, Cheshire

I go to a private school an hour away from home. I quite like school, which sounds funny. I chose to study quite a few creative subjects like textiles and home economics, and I get to do quite a lot of music lessons, too. At my school, in every year there'll be, like, one girl group and one boy group and then each of those is split up into three groups. Everyone has got their own category they're in. It's who you are, really, what you like, and who you get on with.

I'm in a group of six best friends. We all hang out most Saturdays, go to the cinema or just hang out in the park or go for a meal. We talk about everything. I'm quite open anyway but I know my friends know everything about me, especially my best friend.

My family is pretty close. Sunday is family day, which normally involves going for a walk with the dogs, or going for a meal. My sister is a friend on Facebook but I wouldn't have my mum as a Facebook friend because she would use it to research all my friends. Some people don't use the internet correctly so there is an element of danger to it, but you learn to deal with that. Parents think you're awfully naïve about everything, but you learn what's not right and sort it out yourself.

When my sister and my mum are talking it's obvious they think, 'Oh she's younger', so they can talk about anything and expect me not to understand. You just let it slide and say, 'Yeah, I haven't got a clue what you're saying', but you do.

I love Justin Bieber, he just makes me feel happy. I saw him in concert and my best friend practically fainted, she was sitting on the floor and I was like 'Are you all right?'.

I suppose I do spend a bit too much time on what I wear. Obviously you want to look good in front of your friends and make an impression. I like to be a bit different to everyone else.

I can't wait till I'm older, to drive or to go to uni. But I'm happy. If I could give adults one piece of advice it would be calm down, stop stressing.

'My parents are happy I'm making money'

Charlie Allan, 17, Bath

I live in a boring little village outside Bath. When I was growing up there was nothing to do but knocking on doors and running away. Now I work most of the time and go to college. I flip burgers at Schwartz Burgers in Bath; it's better than being a kitchen porter.

I'm studying music technology. I don't play an instrument – it's more like DJ-ing and producing on a computer. Obviously the idea would be to be famous but it's not realistic. Maybe I'd like to work in a studio or start my own label or maybe even do some teaching.

When I'm not working I go to mates' houses or go out in town and go clubbing. The clubs in Bath are not very good but there are a few of them. We put on a couple of nights outside college, running a night in Bristol recently and one in Bath. When I finish school I think I want to take a year out and then probably eventually go to uni.

I guess I don't do much in the house for my parents because I'm not really there; I go to college at 9am and end up getting back at 1.30 in the morning. If they ask me to do something I'll do it for them but it might take a bit of persuasion. We argue about me keeping my room tidy, and making sure I actually go to college. I can be a bit lazy, and if I've worked late sometimes I miss my first lesson. My parents are happy I'm making money but annoyed that I work so late.

It's not hard to get a job – people are a bit too picky. You can get a job if you've got a CV and you make it look good. It's just getting off your arse and getting one. I suppose higher-paid jobs are harder to get, I'm on £4.50 an hour, I work hard so I should get a pay-rise soon. My mate's 19 and was manager at Domino's Pizza and had a BMW – he was all set. It can be done quite easily, you don't have to be academic.

'I do disagree with all the cuts in education'

Bertram Silvera, 16, London

Teenagers these days do get a bad press, but I think we're now less rebellious, if anything. When my parents were growing up in the Seventies there were lots of riots and people experimenting with drugs. One thing that is on the rise in London is gun and knife crime – but still I think it's quite a safe place compared to other cities in the world.

I would probably vote for the Conservative Party because I believe that although austerity measures might seem harsh I think that they're necessary; public spending has been too high in the past and it now needs to be brought down so we can pay our debts in order to get out of recession.

One thing that I do disagree with is the cuts in education; I think education is the one thing that shouldn't be cut as it's one of the ways that people can escape poverty –and an increase in university fees decreases social mobility and means that rich people are able to go to the best universities while poor people are forced into lower-wage jobs.

My favourite subject is economics. I think it's the most relevant subject to our daily lives. It's all about what resources are made and for whom; and these are problems that we all face in our daily lives, wherever we go, and knowledge of the subject is a very important skill which equips us with the tools we need to manage our finances. It's astounding that people don't know what APR means. I think economics should be a core subject.

After my A-levels I want to go to Oxford to do Economics and Management – hopefully after that I'll be working at ICAP as an inter-dealer broker. I've just got a sixth-form scholarship place at Eton. My school now is a comprehensive so it is mixed ability but I think that at Eton everyone will be of such a high standard that I'll probably feel a bit intimidated. Also, I think there will be much more open space; there are less people and many more resources for sport and drama and art. They've even got a fully functional theatre.