"My dad left when I was four and I remember thinking it was all my fault. At school, I went from being a quiet, well-behaved little girl to throwing tantrums and arguing in the playground. I didn't know why I felt the way I did, I was just really angry and confused."
Fast-forward to present day and Sarah*, now 24, suffers from a range of mental health issues, many of which she traces back to childhood.
When Sarah was six, her mother's new boyfriend started to abuse her physically and emotionally. She was so afraid that she felt unable to speak to anyone about her abuser and so it continued for five years, until he and her mother separated.
As a result of what was going on at home, Sarah's behaviour worsened and her grades started to slip. Teachers took a punitive, rather than pastoral, approach.
"My behaviour was taken at face value," she says. "I was quickly labelled ‘the naughty kid’."
Sarah’s challenging behaviour attracted unwanted attention and she was severely bullied by her classmates. This ruined her self-esteem and she became increasingly withdrawn and ostracised from her peer group; the situation amplified as she reached secondary school.
At 15, she was diagnosed with depression and anxiety; at 23, she was diagnosed with borderline personality disorder; and at various points as a teen and an adult, she has been told she has traits of obsessive compulsive disorder (OCD) and bipolar disorder.
Her story is, regrettably, far from uncommon. It is estimated that 50% of adult mental health issues begin before the age of 15, according to a national 2012 report by the Chief Medical Officer, and with 1 in 10 11-year-olds having had a mental health issue at some point in their lifetime, according to a 2014 report, this doesn't bode well for the next generation.
The issues can stem from an uncertain or unhappy life at home or at school, whether that's due to family breakdown, abuse, bereavement or bullying.
Experts agree that both parents and teachers are responsible to look out for the mental wellbeing of a child. But, as children do not necessarily have the awareness or language to express such complex issues, monitoring their behaviour is key.
Dr Bernadka Dubicka, vice-chair of child and adolescent psychiatry at the Royal College of Psychiatrists tells The Huffington Post UK: "Children who are feeling sad may struggle to verbalise their feelings but could show their distress through their behaviours, for example, stopping activities they used to like doing or becoming irritable. Young children frequently show their distress through physical complaints, such as tummy aches and headaches."
Of course, not all children will express themselves in the same way.
"It is important to be aware of children who may not be bringing attention to themselves through overt behaviour problems; quiet children who go unnoticed in class may also be struggling," Professor Dubicka adds.
Take 27-year-old Toby*, who was diagnosed with depression four years ago. His issues also began in childhood, but the signs were markedly different to Sarah's.
Growing up, he describes his family home as "volatile". His parents, now divorced, would argue frequently and Toby would often find himself in the middle.
"I had an awful relationship with my parents," he says. "I always thought their arguments were my fault and in many ways I still do."
Toby says he spent many hours crying alone in his bedroom and, since childhood, has suffered from low self-esteem and sleepless nights.
While he says he inherited his parents' temper at home, he kept his head down in the classroom: "I was scared of authority at school. I never spoke to anyone about how I felt."
Toby longed for the nuclear, Brady Bunch-style family and he is convinced the lack of stability affected him, and his relationships, later in life.
This is echoed by the Mental Health Foundation, which states that having a family that "gets on most of the time" is a key factor in ensuring children's mental wellbeing and preventing issues in adulthood.
But while correlations can be identified in hindsight, identifying potential signs and issues in children today can be more complicated.
Dr Harold Koplewicz, president of Child Mind Institute in New York, says: "It’s common for parents or teachers to be concerned by any number of oppositional or noncompliant behaviours that children exhibit. When we’re deciding whether these problems are really concerning, we have to pay attention to their frequency, intensity, duration and impairment (FIDI)."
That’s why the Child Mind Institute has developed a Symptom Checker which combines clinical experience with diagnostic criteria as a source of information for parents before seeking medical advice.
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Unfortunately for many, help arrives too little, too late.
Toby’s unhappy home life, lack of pastoral care at school and limited understanding of healthy relationships and behaviours, affect him to this day.
"Having the chance to say how I felt in a quiet, considered forum may have helped me open up personally much earlier," he says.
Sarah says she feels "frustrated" by certain missed opportunities for early intervention.
Aged nine, she remembers a one-to-one session with someone she now believes to be a child psychologist (although this is unconfirmed). She was placed on a rewards system, where she put counters in a jar for good behaviour, and had a ‘naughty book’ to log misbehaviour.
"Even with a professional the focus was my ‘bad behaviour’. No one bothered to stop and question why I was acting out," she says.
This is why early intervention is so vital. "Studies show that childhood disorders lead to more severe and sometimes multiplying disorders in adulthood," says Dr Koplewicz.
Prof Dubicka adds: "It is a false economy and devastating for the child to allow unrecognised mental health and developmental problems to persist without early intervention."
For someone like Sarah, these conditions have affected the course of her life. She is currently unable to work - having been fired from her last job at a supermarket because of absences due to her health - and her relationships with family and friends have suffered.
The potential for positive change, with timely intervention, could be unprecedented.
"If someone looked at what was going on at home," Sarah says, "everything could have been so different."
Young Minds Matter is a new series designed to lead the conversation with children about mental and emotional health, so youngsters feel loved, valued and understood. Launched with Her Royal Highness, The Duchess of Cambridge, as guest editor, we will discuss problems, causes and most importantly solutions to the stigma surrounding the UK’s mental health crisis among children. To blog on the site as part of Young Minds Matter email firstname.lastname@example.org
*Names have been changed to protect identities
Useful websites and helplines:
Mind, open Monday to Friday, 9am-6pm on 0300 123 3393 Samaritans offers a listening service which is open 24 hours a day, on 116 123 (UK and ROI - this number is FREE to call and will not appear on your phone bill.) Get Connected is a free advice service for people under 25. Call 0808 808 4994 or email: email@example.com