Mention ADHD and most people think of (a) children and (b) trouble. But Steve Riley is one of a growing number of adults being diagnosed, and what's more, he believes the behavioural condition actually enhances his life.

People who know Riley have long been used to the 38-year-old interrupting conversations to go off on weird tangents. But last October, his wife had finally had enough when, in a serious conversation about them moving home, he completely ignored her and wondered aloud if there was some poo on his shoe. Why, she despaired, couldn't he focus, just for once.

For Steve, it was a light-bulb moment. "Perhaps, I suddenly thought, it's not normal to joke about unrelated things in the middle of a conversation. And perhaps, it also occurred to me, it's not normal to constantly lose my keys, forget things and bring the wrong things home from every shopping expedition – all things that I seemed to be doing more than ever."

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Riley explains that at any one time, he'll be thinking of countless things at once, with his attention flitting from one to another involuntarily. "It's a bit like sitting in front of a bank of TV screens all tuned to different channels. Conversely, sometimes the TVs all tune into the same channel and I become completely absorbed. So paradoxically, not only is it difficult to pay attention to one thing, but it can also often be difficult to shift your attention from one thing to another. This, I would learn, is what leads to the forgetfulness, lack of concentration, poor grasp of time passing and difficulties with prioritising tasks."

It's also what leads Riley to obsess about a particular thing such as a writer or film director, reading or watching their every piece of work for weeks on end, unable to think about much else. Another outcome is Riley's love of loud rock music and cheesy action and horror films, packed with explosions and screaming.

No wonder that, within seconds of Googling his traits, the letters "ADHD" appeared on Riley's computer screen. "Like most people, I'd always associated ADHD with children, but reading the list of symptoms was like reading a description of me. Tentatively, I put it to my wife, who is a speech and language therapist working with children with emotional and behavioural difficulties. Rather than saying, 'Don't be silly!', she looked at me for a moment and said, 'Yes, I think it would be a good idea for you to get checked out.'"

Less than six months later, Steve had a diagnosis. "The first health professional I saw, a locum GP, wasn't convinced. He said I wouldn't have been able to sit still for more than 30 seconds as a child if I had the condition. But that's an outdated and incorrect view and thankfully not one that my own GP had. Instead, she went through a process whereby she eliminated other things that might cause the same symptoms, notably depression and an overactive thyroid gland, and then referred me to a psychiatrist, who focused on whether my symptoms affected me in all my environments and had done throughout childhood."

Luckily, Riley still had his school reports. They all said the same thing – Steve is a clever kid, but forgets his work, doesn't finish his homework and doesn't concentrate.

The psychiatrist confirmed that this, along with his extreme disorganisation in childhood, is typical of ADHD sufferers. "One time, my primary school teacher upended my desk because he was cross about me sneaking something into it. I can still remember his face changing from anger to shock as he watched more and more stuff topple out – rubbish, work, bits of paper, you name it. It was like a comedy sketch."

Perhaps not surprisingly, Riley failed his A levels and then got kicked off a college HND course. But after retaking A levels in subjects he really enjoyed, he passed and got an office job in the civil service. "But I got bored and so at 28, I did a degree in English literature to further my career. I passed and for the last seven years, I've been enjoying working as web editor for Relate."

Not that Riley has been off the hook from his chaotic traits in this role. "In fact, as work has become busier, it's got worse. I was increasingly going into meetings with my boss, realising there have been things on my to-do list for months."

The diagnosis, which finally came last summer, has been a saviour, says Riley. "I now have confirmation that I'm not a lazy failure – I just have a brain that works in a different way. This has been very emotional and I've needed some counselling, but even that's been positive because it's helped me reassess the world as I've seen it for the past 38 years."

The diagnosis also led to Riley gaining government-funded help to find strategies to deal with the more problematic areas – new ways of planning and preparing, wearing headphones to stop distraction, breaking down large tasks and so on.

But, and he doesn't say this lightly, he wouldn't be any other way. "The way my brain darts from one thing to another means I can make huge creative leaps. I come up with good ideas that other people don't think of. For example, in a meeting, I might make a connection between something someone said 20 minutes ago. You could say I have a way of looking at the world that leads to me coming up with interesting, often unique, solutions."

The way his attention and thoughts shift and jump can take him by surprise, too – often cracking him up. "Some of the best jokes come from making odd connections between things that shouldn't connect and that comes so naturally to me that when I once did a comedy workshop that taught methods of writing comedy, I found I already made the kind of juxtapositions they were teaching."

Riley adds that he is rarely bored. "A million things in my head keep me occupied at any one time."

Andrea Bilbow, chief executive of the charity ADDISS (the National Attention Deficit Disorder Information & Support Service), isn't surprised by Riley's attitude. "There are lots of people who tell you it's a gift and there's some interesting research going on at the moment into ADHD's links with creativity," she says, pointing out that the comedian Rory Bremner believes he may have ADHD.

But, she adds, this can be a double-edged sword because ADHD can stop you from being successful with that creativity. "ADHD dramatically increases your likelihood of being out of work and even in trouble with the police, being on drugs and going to prison. It's these negative factors that make it so essential that people get a diagnosis, whatever their age. After all, ADHD is a recognised disability for which you are entitled to get support. But sadly, diagnosis in adulthood remains uncommon because it's expensive and unlikely if you don't seek it out."

Riley agrees that having ADHD has been anything but plain sailing. "But in my case, if I had a magic wand, I honestly wouldn't get rid of it."

The way my brain darts from one thing to another means I can make huge creative leaps. I come up with good ideas that other people don't think of