Animal magic: Craig MacLellan with his dogs / Jim Wileman

When PTSD left ex-soldier Craig MacLellan suicidal, it was his dogs that brought him comfort. Now, his charity provides help for those who face the same challenges.

The day I found myself cowering in the corner of my lounge, sucking my thumb, started out like any other. I had got up to go to work, a good job in IT that I loved. But then, like a bolt out of the blue, I had this overwhelming feeling of everything falling apart, and I suddenly lost the plot.

I'm still not quite sure how I managed to get myself to the GP that morning, but all he did was ask a few questions and sign me off with work-related stress. It's true that I had become a workaholic, and the doctor decided that the solution was a prescription for anti-depressants. But after that, my condition only deteriorated, with panic attacks so severe that very soon, I couldn't even leave the house in daylight.

I couldn't sleep, often staying awake for three or four days at a time. I felt constantly on guard, as if I was still in the army, which I'd left five years previously, and the paranoia was overwhelming. I believed that my neighbours were out to get me and I reported every unfamiliar vehicle parked on our street to the police. My only comforts were my two dogs – Fudge, a chocolate labrador and Jake, a springer spaniel – who I would walk at night.

My wife felt devastated, watching her big, strong, capable husband crumbling before her eyes. She started to suffer from anxiety herself. The GP remained firm that my pills would help me, but they didn't. Friends disappeared quickly and work colleagues took a "pull yourself together, lad" kind of attitude.

About six months later, I decided to take my own life. It was a strange and dangerous feeling, one of calm and peace, and I took Fudge to assess the place I had in mind. But when we approached it, she went rigid. She'd never done anything like it before and I actually said out loud, "I'm not going to do anything, girl," and I kept my promise.

Instead, I decided to call an organisation called Combat Stress, which helps ex-service personnel suffering from mental-health problems, and after a visit from their welfare officer, I was invited in for a week-long, residential assessment. I felt sure I'd end up in a padded cell. But the moment I arrived, a man put his hand out and said, "You are safe now, Craig," and it was so profound and sincere that I'm welling up even now at the memory.

The team of psychiatrists, psychologists and therapists diagnosed me with post-traumatic stress disorder (PTSD). It made sense. At 16, after a difficult childhood, I'd escaped to join the Royal Marines. I loved it immediately, developing massively in confidence, fitness and skills and the marines were more of a family than I'd ever had. In 1989, an IRA bomb was dropped on our barracks in Deal, Kent, killing 11 marines and wounding another 21. It made me reconsider everything, and I went off to do a degree, with a view to a career change. But it wasn't for me, and after graduating at 24 years old and marrying my wife, I signed up again, this time in the army.

Craig MacLellan's canine kit (Jim Wileman)

It felt like coming home, but then came the postings to Northern Ireland. Usually lasting six months, we were expected to live like caged animals behind barbed wire in dire conditions and permanently on a knife-edge of threat. The only time we left camp was to patrol, often on riots, and I saw horrific things that, even now, I can't speak of. Friends were involved in accidents and incidents, and I lost one of them. A policewoman was shot right next to me. To top it all, the politicians were making decisions none of us could comprehend and even those who supposedly supported the British flag seemed to be against us.

Yet despite the inevitable feelings of stress and pointlessness, we were trained to be emotionless. The closest you'd get to letting your emotions spill out was getting drunk with your mates, who'd remind you not to dwell on things. I couldn't even talk to my wife because our calls were monitored.

By the time I hit 30, I couldn't stand it any longer and left to work in IT. I revelled in the small freedoms that my new life gave me – going home to my wife every day, and deciding when I took a holiday. I was happy again.

But here I was, five years later, realising that I hadn't escaped my past quite as neatly as I'd hoped. Following my week-long assessment, I was invited by Combat Stress on a series of fortnight-long cognitive behavioural therapy (CBT) sessions, which were brilliant, although sadly I was let down by my NHS psychiatrist, who was supposed to be backing it all up but regularly missed appointments, triggering my anger and feelings of low self-esteem.

This meant that a year later, I still hadn't moved on as much as everyone had hoped, and was invited to a more intensive, six-week residential course. It had been clear from my clinical notes that the dogs were now my linchpin, and so I was allowed to bring Fudge into treatment with me, with a view to slowly weaning myself off what was essentially a comfort blanket. What happened next was amazing. Fudge not only helped facilitate my therapy, but that of all the other 16 men, too. It started with Fudge ambling round the room and somehow finding the person who needed the most support. I don't mean responding to tears or outbursts of emotion, but those who were suffering silently and didn't even think it showed. Just by quietly sitting next to them, allowing them to stroke her, Fudge seemed to find a way to get them to open up. Fudge even started interacting with people in need in the TV room. Then she started scratching at their bedroom doors.

It was clear to both the staff and us that Fudge had made a profound impact on the course and outcomes of the therapy, and because I was in a stronger place emotionally, I thought I'd see if I could take the blueprint of what had happened and somehow roll it out.

It didn't take long for me to discover just how important dogs are to men who've been in the forces. Dog handlers recounted how they would share their sleeping quarters with their dogs rather than putting them in kennels because of the comfort they gave them during difficult times. Meanwhile, countries including America, Canada, Australia and Holland had, I discovered, long been using assistance dogs for ex-military with mental-health problems. Why isn't the UK doing anything, I wondered, when we are apparently at the forefront of animal therapies?

So in 2012, with the support of Combat Stress and two universities, I started up my own charity, Veterans with Dogs, to provide assistance dogs for veterans with trauma-related mental-health conditions. It's early days, but we've already got five assistance dogs for ex-military with PTSD, in addition to Boo, my own assistance dog.

Unlike Fudge, who focused on everyone, these dogs are there exclusively for one individual, and what they can achieve is mind-boggling. Boo, for example, physically gets me out of bed in the morning, even on days when I struggle because I'm feeling so low. She then opens the kitchen door and gets my medication.

Equally important are the grounding techniques. When I wake from a nightmare, for instance, I just shout out the word "light", and she switches it on. And if I sense a panic attack coming on, I have a safe command that means I can kneel down and she will jump up and put her paws round my neck, a physical sensation that helps me calm down quickly, wherever I am. She has a means of reducing my hypervigilence and if I'm in a public place where I can't cope, I give her the command to get me out. Thirdly, there's the comfort factor. Indeed, we know from research that physically touching not just a dog but any animal can release good endorphins.

Looking back now to that awful day in 2007, it seems incredible that a dog saved me. Yet that's what happened. Now, five more veterans have benefited, saying their dogs have had a life-changing effect. We now have a long waiting list, and it is my hope that dogs will be able to help many others just as much as they have helped me.

Interview by Kate Hilpern