Young adulthood is a turbulent time for anyone. The hormones, the acne, the first loves, the pressure of exams, and the seemingly endless identity crisis about what you're going to do with the rest of your life. It's a big and difficult time of changes and transitions; and that's without throwing a mental health problem into the mix.

There are also the well-documented problems with the transition from Child and Adolescent Mental Health Services (CAMHS) to Adult Mental Health Services (AMHS), to contend with. But how exactly is this affecting teens on the cusp of adulthood – and what can be done to make things better?

For 19-year-old Rebecca, that tricky transition began two years ago, when she was hospitalised with depression at the age of 17. "I was too old for the children's hospital, so I was sent to an adult's hospital – but that felt even more unsuitable," she says. "There were a lot more restrictions on me in the adult hospital; I couldn’t go anywhere without someone being right next to me."

When she was discharged from hospital, several months before her 18th birthday, Rebecca then found herself in mental healthcare limbo. "They said I was too old for CAMHS but too young for AMHS, so there was this massive gap where I couldn't get any support," she says. "It was really difficult because I had my exams at school, and I just wasn't getting any support for my anxiety and depression. I resorted to medication because they weren't going to bother doing anything else, but it shouldn't have been the only option."

In 2012, young people's mental health charity YoungMinds ran a campaign to improve transitions from CAMHS to AMHS, and continues to do policy work in this area. "That lack of continuity of care because you're waiting can be really damaging," says Dr Marc Bush, Chief Policy Advisor at YoungMinds. "It's also the period of time where you're at increased risk of self-harm or suicidality."

This was strikingly true for 19-year-old Nikki. First referred to CAMHS at the age of 14, following a traumatic incident, Nikki has a diagnosis of Borderline Personality Disorder (BPD), and was under the care of CAMHS until shortly after her 17th birthday.

"I don't think I felt ready at the time, but I wanted to try. The person I was seeing was about to go on maternity leave, and I'd have been too old by the time she came back. I guess she was trying to lessen her caseload," she explains.

When, six months later, Nikki felt unable to cope on her own any longer, she found herself caught in the same limbo as Rebecca. "It had been six months and three days since I'd been discharged from CAMHS, and my GP said I could only be referred back if it was within six months," she says. "If they re-referred me from scratch it was going to be an 18 weeks waiting list, and by that point I'd be too old anyway, so they said there was no point."

Of course, with three months to go until her 18th birthday, Nikki was also told she was too young to be put on the waiting list for adult care. "I didn't feel taken seriously as a young person. It was really horrific. My mental health was really bad at that point, I really wasn't coping, and they just told me to get by," she says.

"I actually took an overdose a few days after my 18th birthday, went to A&E, and said 'please can you help me? I'm not coping.' They finally referred me for an assessment, but the community team said they couldn't take me onto their service because I was going away to university within the next three months."

Nikki now campaigns with Rethink Mental Illness and is training to be a mental health nurse. She believes a change to the age of transition would help ensure young people got continuous care at such a crucial time in their lives. "It's not like you turn 18 and bam you're an adult; it's just not realistic," she says.

Indeed, there is now a move in some areas towards services for 0-25 year olds, as highlighted in the Department of Health's 2015 research, Future in Mind. "For us, a big solution is guaranteeing continuity of support," explains Dr Bush. "In practice, most young people don't end up with any kind of [treatment and transition] plan, even though the ambition of Future in Mind is to provide continuity of care up to 25."

But, even where CAMHS services continue into young adulthood, the geographical variations across different NHS Trusts present further problems for students like Nikki. As Rachel Piper, Policy Manager at charity Student Minds, explains: "university students are a vulnerable group, and the complicated transition between CAMHS and AMHS is complicated further by students moving to new areas of the country to study. It's a time when there's a lot of different things in flux, and NHS services are not currently adapted to the transient nature of student life."

A major problem, she adds, is the fact that students can only be registered with one GP at a time. "It means you can spend a significant amount of time living in an area where you're not registered for your GP – and, although you can get support as a temporary patient, it's not necessarily adequate for continuity of care."

Between 2012 and 2013, Student Minds carried out a research project, University Challenge, looking at students' experiences of eating disorder care at home and at university. "In our survey, 96% of the [healthcare] professionals we asked said they felt students didn't get specialist care quickly enough, and 92% said students' treatment was negatively affected by the transition from home to university," Ms Piper explains.

"We also found that 83% of students had problems accessing support from their home GP, and many reported being refused access to specialist services – ranging from blood tests to psychological support – if they were registered as a temporary patient."

Although it focused specifically on young people with eating disorders, Student Minds believes many of the recommendations from that report can be applied to student mental health across the board. "The first recommendation is that appropriate support is put in place at university before a student arrives. If someone's been discharged from a specialist service because they're moving, we think this should be standard practice, to avoid their health deteriorating in what is often an uncertain period of time," Ms Piper explains.

"Under resourced university services are already doing a great job in supporting students with mental health problems, but what we need is a joined up approach where the NHS and the university are collaborating to provide the best care for students. There should be clear communication across all the organisations that are involved with someone's care," she adds.

For 20-year-old Karl, who's a media ambassador for Student Minds, university was the first place he was able to access effective support for his severe depression – after a negative experience of CAMHS put him off engaging with AMHS. "CAMHS felt more like a hindrance than something that was helping me, so after I was discharged on my 18th birthday I felt like I was free," he says.

"I just remember confusion about the transition. I vaguely remember getting calls from adult services and ignoring them; I simply took myself off the map. After discharge from CAMHS I took a gap year – which consisted of me staying in bed all day, every day, sat in a dark room. Needless to say I wasn't in a good space at all."

It took another, very serious depressive episode during his first year as an English Literature student for Karl to finally get the support he needed. "It was by far the darkest time of my life, and problematic coping strategies emerged – an insane workload, excessive consumption of alcohol. My flatmates knew something was amiss by looking at me – I wasn't showering or looking after myself in any meaningful way – so they booked an appointment with my GP on my behalf," he says.

"Things reached a head after a month or so, as I caused a disturbance at a university bar. The police were called, I was detained under section 136, and hospitalised. It was a tremendous relief because I was sure I would get some form of treatment away from the pressures and alcohol of university," he adds. "While I was there we were able to get the medication cocktail right, to get rid of alcohol, to lighten my workload, and come up with strategies for maintaining my wellbeing. I saw my local mental health team for a while after leaving hospital, and my university, the University of Kent, has been great in terms of support."

As all these young people have found, access and quality of support vary across the country, but there are areas of good practice that both Student Minds and YoungMinds hold up as examples of how transitions should work. "The one that everywhere quotes as an area to look at, and has been for about the last decade, is Birmingham," says Dr Bush. "It was one of the first areas to co-commission from 0-25, and to have a lead specifically for transition work across special educational needs, disability, and mental health."

Student Minds also highlight how innovation in technology, and the use of peer support groups like MyAPT, can be really positive ways to engage with young people at this turbulent time. The NHS's Support, Hope and Recovery Online (SHARON) programme is one such digital tool, designed for young people with eating disorders, which Ms Piper says, "has a very recovery focused atmosphere and means patients can go online 24/7 for support."

Ultimately, the solutions appear to boil down to engaging and taking young people seriously; services that are accessible and user-friendly; clear lines of communication between children and adult services, both at home and university; and a more flexible approach to when adolescence ends and adulthood begins. At such a pivotal time in people's lives, the right continuity of support really could make all the difference.