Bipolar disorder is a rollercoaster of emotion for sufferers and family alike but can stem cell advances offer new hope?

Instant gratification. Cairns worked full time but his father had Parkinson's and his mother was developing dementia, so he visited daily between split shifts. He hadn't had a day off in 18 months.

Cairns is open, gregarious, but watching him recall what happened next is like watching the petals of a flower curl inwards at dusk. He doesn't want to remember. He was at work. Started shaking. Everything was jumping from place to place. He tried to strip off his clothes. "I wasn't able to control the way I was acting and feeling," he says. "I didn't lose control of my bodily functions but of my mind. It frightens me to remember it."

Following emergency hospital admission, Cairns was diagnosed with bipolar disorder, a psychiatric condition once labelled 'manic depression', and often depicted in popular dramas by deranged-looking women straight out of Mr Rochester's attic. But it has become almost fashionable recently, with a number of celebrities, including Stephen Fry, and more recently Catherine Zeta-Jones, identified as sufferers. Fry, in particular, has urged more positive understanding, drawing links between the 'manic' phase of his illness and his creativity. But what is the reality for ordinary people, in ordinary jobs, living with the disorder?

The condition causes distressing mood swings between two 'poles': up and down. The 'up' or 'manic' periods are sometimes described as elation but are actually more commonly periods of agitation, marked by anxiety, sleeplessness, driven behaviour, and sometimes shopping sprees and delusions of grandeur. This is followed by a plummeting mood, and indeed for many people it is depression rather than mania that will define their illness.

Those with a more serious form, causing frequent swings between two mood extremes, suffer from Bipolar 1. People who suffer mainly depression but have had at least one incidence of 'mania', have Bipolar 2. As many as one person in 50 will suffer – twice the number who have, say, diabetes. "These are very common conditions," says Dr Andrew McIntosh, a consultant psychiatrist and research fellow in Edinburgh, and medical adviser to Bipolar Scotland.

Dr McIntosh believes we are entering a significant period in the understanding and treatment of psychiatric illnesses. Other branches of medicine have made significant advances by taking biopsies from patients and studying individual cells. "But of course, the brain isn't accessible during life," he explains, " and that's been a massive limitation. But technology has recently become available where you can take skin cells, develop them into stem cells, then reprogramme them into virtually any kind of tissue in the body, so you can actually reprogramme them to become neurons. What we're looking at is using this as a means of investigating psychiatric disorders in a test tube for the first time."

McIntosh is currently examining genetic links in families. "We are looking at people between 16 and 25 who have a very close relative with the illness and following them over ten years. A few will develop bipolar and we're able to see if we could have predicted it with brain scans." A number of genes linked to bipolar have already been identified but there could be hundreds and, at the moment, it looks as if they might only slightly increase the chances of developing the disease. But using MRI scans, researchers have already found differences in brain structure and function in people with bipolar disorder. "A part of the brain called the pre frontal lobe is a bit smaller, and bits of the brain that are involved in processing emotion, particularly a part called the amygdala, seem to be more active – too active, if you like."

Within 48 hours of being taken into a Glasgow hospital, George Cairns was diagnosed with bipolar for the first time. He was 53 years old. He had suffered bouts of depression throughout his life, approximately every three years since his late teens. (It's not uncommon for the two illnesses to overlap but accurate diagnosis is important because anti-depressants, most of which increase serotonin levels, can actually trigger mania in some patients.) Cairns' most serious depression had come a few years earlier when, after 27 years in the ambulance service, he attended a fatal accident involving a young person. He had attended many over the years, but this time, something snapped. "The memories of it never left me for months. I was very tearful." Cairns tried returning to work but eventually took early retirement on health grounds.

For his daughter Gillian, then just 17, it was devastating to see her father so unwell. Gillian runs a nursery and, like her father, is friendly and outgoing. You can feel their connection in conversation; the heat of their experiences has soldered them together tightly. An only child, Gillian used to argue constantly with her mother and it was her father who was her champion. "I idolised my dad," she says. That changed after his illness. Suddenly, she and her mum were thrown together, changing the family dynamic.

Gillian describes her emotional reactions with such raw honesty you might think it would be hurtful for her listening father to hear. Yet each seems to completely understand the other's position. "I felt I'd lost my dad," she admits. "Like any daughter, my dad was my hero. All of a sudden, he wasn't. He was just human." Her words highlight a fundamental truth about mental illness: subconsciously, we blame the patient in a way we never would with other diseases. Mental illness is their weakness rather than their misfortune. Gillian had never guessed George suffered from depression in her childhood so the shock now was almost like bereavement.

Her father was gone and she distanced herself from this impostor left behind. "When he was very ill, I didn't call him Dad. I called him George." She remembers visiting him for the first time. "I thought, this is a mental institution.

"A nurse actually took me into a room and said, 'Tell me what you're thinking.' I said, 'My dad's gone nuts.' She said, 'It's not about that,' and she did help, but I felt like I'd lost him."

George is very quiet as she talks. Did he notice when she stopped calling him Dad? He shakes his head. It must be strange to hear that. "Yes, it is but I don't remember it." He had, says Gillian, retreated into his own little world, an almost child-like state. "You knew who we were," she says, turning to him. "But there was no recognition. No interaction. I was holding your hand but you weren't gripping it as you would normally."

George eventually recovered enough to return to employment, this time as a carer. Gillian married, a relationship that would ultimately break down. Perhaps, a counsellor suggested, she married quickly to escape the situation? Possibly true, she admits. She only knows that when George's manic episode happened seven years ago, she felt let down again. For such a large part of her life, her father had been solid rock. Now he was crumbling. She protected herself with a veneer of anger. "I really wanted to say to him, 'I feel as if you are being so selfish.' I know it wasn't selfish but I had just had a baby, was getting myself back on my feet, and all of a sudden ..." When did "George" become "Dad" again? "Truthfully?

Not for a long time. You're talking three years where it just didn't feel the same."

Though she doesn't have the disorder herself, Gillian has joined Andrew

McIntosh's research project, and volunteered at Bipolar Scotland to show solidarity with her father. But she wants her initially negative emotions to be reassuring for other families. Perhaps the toughest question to ask is whether those closest to patients can trust them. Did she, for example, trust George with her daughter, Isla? She hesitates. "I lived in Dalkeith at that time and my dad would say, 'I'll drive through and take Isla and she can spend the night with us.'" She glances at George. "I don't think I ever told you, but I remember saying to Mum, 'I don't want him to.' It wasn't that I thought he was going to do something silly. It was just the scary thought that he might not know. It wasn't that I didn't trust him. Well, I suppose it was that I didn't trust him to be honest."

But the trust returned. George looks after Isla regularly. Originally, he was put on lithium. It's one of the most effective medications but can cause serious weight gain and George put on over three stone. He has just completed a phased withdrawal, though he remains on anti-depressants, and is now determined to lose the excess weight. The best illustration of how much his condition has stabilised is perhaps the way he coped with his parents' deaths, because bereavement is considered a potential trigger for relapse.

His mother died just last month, but George felt relief as well as loss because he recognised that dementia had robbed her of dignity. "She was beautiful looking in death, honestly. Really beautiful. I was happy for her. My mum and dad enjoyed the dancing and I know she went up there on the Saturday night and danced with my dad. That's what I felt. So there you go."

A house in a small Scottish town. A woman – let's call her Sarah – lives with husband Alex and son Jamie. Anonymity is part of the bipolar story still. Celebrities may acknowledge the condition – it almost enhances their mystique – but Sarah is a teacher. "If it weren't for that fact, I would definitely want to be identified. But it's the people who don't understand … the waves it would make … the unhappiness it could cause in a small community. You don't want somebody to say, 'This woman is mad and she's got children in the room'." Why would they? Because the popular depiction of bipolar has been the rather crazed performance of Stacey Branning's mum in EastEnders. "The soaps make it a bit too hysterical and dangerous," says Sarah. "It's a woman running round in her nightie with an axe." She barely pauses. "I mean, I only do that at Christmas."

Sarah is articulate, humorous. Always anxious as a child, she would get over-excited then plummet, her downs casting shadows on her life that seemed darker, deeper, longer than other people's. The most extreme lows began in late teens – a common experience – when she went to college. She was extremely close to her mother and would phone three times a day. But this was no ordinary period of homesickness. "I remember trying to join in, going on a walk with a club, and there was a lorry, and I thought, 'You know, I could just jump in front of that.' I felt it that strongly."

She studied design and loved it, was top of her class. Her final project kept her awake for three days and nights, bombarded by ideas. When she finally tried to sleep, she experienced a strange waking dream. There were scarab beetles flying around the bedroom of her flat. She remembers looking at them, thinking: "Whooh, powerful stuff." But as soon as her show was displayed, she plummeted. "I was in pieces. I could not stop crying. I was a mess and then I slept and slept and slept."

It was never talked about, but in all probability, this was Sarah's genetic inheritance. Several members of her family had similar problems, including her father. He was a highly successful man with a responsible job, but he fought anxiety and depression at a time when nobody dared mention psychiatric illness. "People then would have been terrified of saying anything," explains Sarah. "He would have probably lost his job."

Her father struggled without medication, only once being referred to hospital out-patients. Sarah's most vivid memory was in her late teens. "He came up to me, put his arms round me, and cried, and said, 'I'm really struggling at the moment.' It was the only time I saw him in tears.

He wasn't like that." Her mother used to tell Sarah her dad was the strongest person she knew because he simply battled silently. "He was a brave man who had done a lot. He was in the Second World War, was incredibly bright, very creative, had a responsible job. People think you must be weak if you have this problem but there's no way he was weak."

Sarah knows that if she passed the illness on to Jamie it would make her sad. And yet, she hates the thought her father would blame himself for her condition. "What's one thing?" she asks. "What else did he give me? He had everything … he was a very handsome man, successful. He had my mum and a family and we all did OK." But more importantly, bipolar made her who she is. "Any difficult things you go through carve out a little more of your personality and deepen you and also help you empathise with other people."

She laughs. "Don't get me wrong … I don't want any more bad times. But if I could just get agreement that I've had what I've had and don't have any more."

Interestingly, Sarah has in a way recreated her parents' marriage. Her mother was a positive person who balanced her husband's negativity, and Sarah, too, has gravitated towards someone positive. Alex is Tigger to her Eyeore, she explains. For many years she had no specific diagnosis but her depression worsened after Jamie was born and became acute after a hysterectomy. It was then she began medication which she will probably take for the rest of her life. She's 51 now but has been stable for the last ten years. Like George, against expectations she coped well with her mother's death. They were so close, she had dreaded losing her mum all her life. "But sometimes it's the big things you cope with because you've had to cope with so many big things before."

Of course, her condition hasn't disappeared. There are still bad days, when Sarah retires to bed. But it's manageable and at least it has a name. Before that, there were difficult periods in her relationship with Alex, she admits. "It was a lot of strain on him. I wasn't an easy person to live with. I was very depressed, very irritable, just hard going."

The most frightening thing about mental illness is that in the thick of it, your judgment is affected. "You can make family life very difficult.

People can walk out of marriages because they can't see things in the normal context. There's a danger that you can lose what you love the most."

Yet now, the love and solidity within Sarah's family is very apparent. Jamie is a bright, friendly teenager, quite protective of his mum. It used to make him upset when she was upset, but now he understands the cause. Alex used to tell him that Mum got a bit sadder about things than she should but he mustn't worry because she would sleep for a bit and then be fine. He accepted it because children do.

"She seemed different from other mums and dads," he explains, "more lively." She got a bit twitchy at times, agitated over small things and jumpy if he dropped something. "But I never really thought, 'Oh God, I don't want to go home.'" He smiles. She was better than some other parents. He wouldn't swap, then? Nah. When he was small, Sarah would sometimes explain to Jamie that she was a bipolar bear today. Jamie, enchanted by the idea, asked if he could be one too. He made her a miniature bear she still has.

Alex is a thoughtful man, quietly spoken and considerate. "I found it difficult to understand early on," he admits. "We could be out for the evening and she would be on tremendous form, sharp and witty, but next day she would completely crash. There were times when you didn't know what you were coming home to. Would she be depressed, or slightly agitated and picking fault in everything?"

Positive people often take a "pull yourself together" view of depression. When he's alone, I ask Alex why he didn't. He pauses. "We are very much soulmates," he says, which in a way, answers every possible question. Also, Sarah has always been very good at saying sorry. Perhaps someone less volatile would be easier to live with but he is attracted to Sarah's energy, her tremendous rushes of enthusiasm. Not that either of them would say it has been easy. Sarah remembers when her medication started working and the consultant asked Alex how he thought she was doing. "Yes," Alex said, "I think I've got the woman back that I thought I'd married."

Too often, psychiatric conditions are seen as a threat to the public when, in fact, most sufferers are more a danger to themselves. But effective medication is vital and, until now, has been hit and miss. "Not everyone responds to medication that well," explains Andrew McIntosh. "Around a quarter will have chronic and intractable symptoms that are persistent and don't go away easily." Even those who do control the condition often have low-level problems connected to concentration and memory.

Medication has hitherto been tested on animals. But animals don't suffer human psychiatric disorders. Now, the ability to take and examine cells from patients themselves means the understanding of such conditions is about to take a leap forward. Licensing new drugs is a slow process but the prospect of progress within the next ten years for people like Sarah and George is real. "It's incredibly positive," says Andrew McIntosh, "and we're very excited." n

For information, advice and self management training contact Bipolar Scotland (0141-560 2050, www.bipolarscotland.org.uk)

• This article was first published in the Scotland on Sunday on May 22, 2011