As British soldiers return from Afghanistan and Iraq suffering from post-traumatic stress, we talk to them about the toll it's taking on their relationships.

September 3, 2009 - Peter Doolan must have stood out as he approached his small Victorian house at the edge of Dereham, in Norfolk, on a June morning in 2005. His wife Rachel was just leaving to take the children to school and looked up to see her husband standing in front of her dressed in torn desert fatigues, with sand from Iraq in his hair and his comrade's blood all over him.

Doolan, a Territorial soldier in the East of England Regiment, had come home to East Anglia for a two-week break from the war in Iraq, what the military call R'n'R (rest and recuperation). Less than 24 hours earlier he'd been in the middle of an intense firefight. His unit was protecting a convoy making its way north from Basra to resupply a base in al-Amara. They were attacked 11 times on the journey and lost three men.

"One of the drivers was killed and we had to take his body with us in our wagon," Doolan recalls. "We hadn't brought any body bags with us, so when we moved him I got his blood all down my left side."

Doolan can still barely talk about it, because the adrenalin kicks in and aggression builds up and there's a danger that he will lose control. I find myself staring into the face of a soldier who looks as though he is in the middle of combat.

Now 29, Doolan is one of several veterans of Iraq and Afghanistan with whom I've spent time over the past year as I've been making a Channel 4 Dispatches documentary about the hidden cost of the wars. These soldiers' lives have changed dramatically as a result of their traumatic experiences and are just as disabled as the limbless casualties our sympathy (and charity) tends to focus on.

As the war in Afghanistan intensifies, more young men will find they've returned to a world that for them has changed. People such as Martin Lindley, 23, an explosives expert from the Royal Engineers who did his tour of duty in Helmand province in 2007. Since he's been back he drinks a litre of vodka a night to get to sleep. He told me that he "just doesn't feel safe any more" and he fears someone will kill him as he sleeps. Then he showed me the machete he keeps by his bed as protection.

However, few of the people I've spoken to are as affected by their experiences as Peter Doolan. The violent nightmares started when he went back to Iraq and they haven't stopped since. Doolan says that he could have been treated then, but that he was told he'd get over it: "Because I didn't have a gunshot wound or a missing limb nobody did anything." But he also takes some responsibility for not insisting on treatment. "Perhaps I could have pushed it," he says, "but when you're serving it's embarrassing to admit you're having this kind of problem."

It's unclear whether early treatment would have prevented what came later, once his tour of duty finished. Having been together since they were teenagers, Rachel Doolan was used to watching her husband make the gradual adjustment back to normality after a stressful action, but this time it was different. When she talks about it she does so with a lightness in her voice that disguises something truly upsetting.

"Things got very unnormal," she says. "Usually I'd give him time to get over it, but he just never did that time, it just never happened. He wouldn't wash or shave, he wasn't interested in the kids or anything. One night he just disappeared with his full Army kit on. Half of Dereham police force were out looking for him, they even used a helicopter. Eventually he handed himself in. When the police brought him back he had all these twigs and daffodils in his helmet and mud all over his face." While she's telling me this, Doolan sits on the kitchen worktop, chuckling occasionally. Humour has become a tool they both use to cope with his condition. Somehow, it seems to normalise a thing that would have destroyed most families. Rachel says: "When these things happen I cry and get angry and upset, but afterwards if I don't laugh about it there's no way through it, I'd be a nervous wreck."

The couple have three children and their family have made an extraordinary adaptation to accommodate Doolan's severe post-traumatic stress disorder (PTSD). Upstairs he shows me his middle boy's bedroom. It looks like the normal eight-year-old's room, except that it's Doolan who sleeps under the racing-car duvet, not his son. "I can panic-attack in my sleep and hit out," he says, "so I can't sleep with anybody in case I injure them. When I have a nightmare I'll be sick as well, I'm always running to the bathroom. And the sweats, I have to change the sheets and shower during the night. I haven't shared a bed with Rachel for three years." She is standing in the doorway listening, with a slight smile. "It's not easy to deal with," she says, "but you get used to it. It becomes routine."

Most relationships disintegrate under much less than this. A more typical story is told by Danny McEneany. He went to Iraq six months before Doolan and, like him, his breakdown started as soon as he came back. Once his relationship fell apart, the consequences were all but catastrophic.

A sergeant in the Royal Dragoon Guards, McEneany, 36, had been in the Army since he was a teenager. He'd seen service in Northern Ireland and the Gulf War, but it was the tour of duty of Iraq in 2005 that changed him for ever.

McEneany was stationed in al-Amara, six hours drive north of Basra toward Baghdad. Insurgency was then at its fiercest, but the British were trying to take a passive law-enforcement role. Inside their base the soldiers came under habitual mortar fire with only prefab buildings for protection. McEneany felt like a sitting duck.

"We got hit every day, sometimes three times a day." Like Doolan, his anger rises as he recalls his own trauma, but it's more controlled. "We'd hear ‘pop', ‘crump' and dive out of bed and sit on the floor in our underpants with our body armour on, just waiting. You think it's like a lucky dip, ‘Is this one going to hit me?' "

But it wasn't simply the fear of being hit by a mortar that got to McEneany, it was also the inability to do anything about it.

"They talk about fight or flight," he says, "you're not running and you're not fighting, you're just sat there waiting . . . no control over someone's actions, you just want to f***ing do something. Then one day I opened the door and heard one coming straight for me. I dived on the floor and thought ‘This is going to hurt' but it passed. I got up. I had changed then."

When McEneany got back to his barracks in Germany it seems that the war was continuing in his head. He still thought he was under threat. He became paranoid, believing that Muslim fanatics were going to kill him as he slept, so got hold of a gun to defend himself and his family.

His wife tried demanding that he seek help from his army unit but, like many soldiers, he wouldn't consider it, believing it would be the end of his career. Eventually his wife left him and McEneany moved in to accommodation in the sergeants' mess.

As he's telling me this, he picks up a heart-shaped cushion from his bed and points out a small hole in it. "When she threw me out I packed my kit up and the gun came with me," he says. "One night I was sitting in a chair with the telly on and I thought ‘I wonder if this thing works?' I put a magazine on, cocked it and just thought ‘F*** it' and put it to my head. I'd lost everything." He pulled the trigger but moved his head at the last moment. The bullet went through the cushion and ricocheted round the room. McEneany eventually ended up on a military psychiatric ward, but only after he'd got into a series of near-fatal confrontations with camp guards and other soldiers. PTSD was diagnosed, but he was charged with possession of an illegal firearm. At his military tribunal, he was dishonorably discharged and sentenced to five years in jail.

The sentence was later reduced by a civilian court, but McEneany still spent two years locked up with no treatment for his condition. Soon after being released last year, he started a relationship with a new partner, Jools. "I couldn't believe he was sent to prison in the first place," she says. "I thought he'd be reprimanded and helped."

In many ways Jools is now McEneany's carer. When I ask what he'd do without her, she replies: "He'd be back in prison. He'd have found any excuse for a fight and that would have been it. He sees threats everywhere, he's ready for anything."

Like Rachel Doolan, Jools is taking an unreasonably large responsibility for keeping her partner together. Both men are practically housebound, unable to perform the simplest tasks because of the risk that they may have a violent outburst. With the help of doses of calming drugs Doolan is able to make the bus journey to college in Norfolk three days a week, but he clearly finds it exhausting. If the bus gets too full he'll get off because a panic attack will start and he'll vomit.

This burden has fallen to Rachel and Jools because treatment for veterans suffering from PTSD is patchy at best. Unlike most veterans to whom I've spoken, McEneany is now receiving some specialised treatment from the NHS, but it's restricted to a limited number of sessions. Because he had a good GP, Doolan's condition was diagnosed soon after he returned from Iraq and his treatment was handed over to a charity, Combat Stress. It provides him with residential treatment courses that last a couple of weeks at a time, but as a charity its resources are limited and demand is high and getting higher.

In America, there is a more systematised approach. Only last month the US Army also announced that it plans to require all 1.1million of its soldiers take intensive training in emotional resiliency - the training will also be available to their relatives.

Unlike Doolan and McEneany, most soldiers who develop PTSD do so long after they've seen active service, sometimes even 20 years. For many families it's a psychological bomb waiting to explode.

Dispatches: Battle Scarred, which is directed by David Modell, will be on Channel 4 at 8pm on Monday.

For more videos, including a clip of Peter Doolan explaining his condition, go to: www.channel4.com/battlescarred

The Times