There has been a “significant increase” in the number of UK veterans of the Afghanistan conflict seeking mental health treatment, says a charity.
Combat Stress said it had received 358 new Afghanistan veteran referrals in 2013, a 57% rise on the 228 in 2012.
The charity, currently supporting more than 660 Afghanistan veterans, said the issue would become heightened as UK forces prepared to leave the country.
The government said it had invested £7.4m in mental health services.
Combat Stress said it had found that veterans generally waited an average of 13 years after serving before they sought help, but this had fallen to an average of 18 months for Afghanistan veterans.
The mental health charity said its total caseload of more than 5,400 veterans across the UK was the largest in its 95-year history.
BBC defence correspondent Caroline Wyatt said there was now far greater awareness of psychological trauma than in the past, which could explain the rise in referrals.
It could also be the case that the stigma around seeking help for mental health issues has diminished, she added.
She said: “The charity says it is a small but a significant number of veterans who are battling these hidden psychological wounds that, if they don’t seek help, can get far, far worse and be far harder to treat.”
Stephen Coyle was a corporal clerk in the Adjutant General’s Corps. He did three tours of Afghanistan and suffered post-traumatic stress disorder caused by being under “constant stress”.
The 28-year-old, from Bootle, Merseyside, received counselling from charity Talking2Minds after suffering for about a year.
He said: “I became emotionally numb and distant, as in, if I didn’t feel, I couldn’t be hurt. I was trying to push being positive all of the time and hide my feelings.
“I could bottle up a lot, I did bottle up a lot, so when I did go, that was it, I was very sad and in a deep and dark place.
“I was not sleeping, constantly going over what was making me sad, not finding anything to be happy about. Looking at my little boy, who I adore, and still not being happy.
Post-traumatic stress disorder (PTSD) can affect anyone who has experienced a traumatic event such as military conflict, natural disasters or serious road accidents.
Symptoms can include flashbacks, poor sleep and a change in mood.
Combat Stress offers free clinical treatment programmes at its specialist centres, community and outreach support, occupational therapy and a 24-hour helpline.
Its chief executive, Cmdr Andrew Cameron, said: “A small, yet significant number of veterans who serve in the armed forces each year continue to relive the horrors they experienced on the front line.
“Day in, day out, they battle these hidden psychological wounds, often tearing families apart in the process.”
He said 20% of veterans were like to suffer from mental ill health and needed specialist support, adding that the charity was planning to provide services at the same level for the next five years as demand was not expected to fall.
“We cannot allow the ex-servicemen and women who suffer from the invisible injuries of war to go unnoticed and untreated. This is an unnecessary drain on society and our veterans and families deserve better,” he added.
“Whereas now, I look at him, and I’m happy, sunshine, that’s all I can describe him as, bright yellow sunshine. That’s my little boy, and that’s the difference.”
Lewis McKay, 26, on the effect of post-traumatic stress disorder
Dennis Carlon, research psychologist with the charity, said he believed it was not just those who had recently returned from conflict who could be affected.
“People have had it for donkey’s years,” he told BBC Breakfast. “They’re coming forward now because they’re seeing that there is help out there which wasn’t there before.”
The Ministry of Defence said it had invested £7.4m to improve mental health services and ensure they were available for everyone who needed them.
A spokeswoman said: “We want to further reduce the stigma of mental illness, encouraging even more people to come forward, and we will continue to work closely with Combat Stress to help veterans access the wide range of support available.”