The Smiths made music between 1982 and 1987. In band years that's a relatively short period of time, but it was five years that produced four revered albums and stoked a mythology around the band's singer Steven Patrick Morrissey that endures 30 years on. For many they were the last great British band; Morrissey is arguably the last messianic figure (Mozziah) in British pop who hasn't died or become irrelevant.

The fans who followed the band first time around – and subsequently Morrissey's solo career – are now in their early forties. For them, the memories are heavily scented with nostalgia. But the appeal has crossed generations; there's a whole section of the fanbase who were not yet born when Morrissey appeared on Top of the Pops brandishing gladioli and wearing NHS spectacles.

What unites them is a feverish devotion to the man and his music. Many will be in Edinburgh on 30 July to see him perform at the Usher Hall, after which it might entertain them to stick around for two Fringe shows that delve into the psyche of Morrissey fandom: Amy Lamé's Unhappy Birthday and Half a Person: My Life as Told by The Smiths. The latter is about a twentysomething Londoner whose existential grind takes place against a soundtrack of Smiths songs. The lead character, William, is the archetypal Morrissey fan: awkward, endearing and mildly obsessive. It's a particularly virulent strain of obsession, being a Morrissey fan, as comedian and actress Amy Lamé (right) discovered when she first came across The Smiths as a teenager in New Jersey.

'There was something about him that represented something I wanted, I just didn't know it yet,' she recalls. 'He said it was OK to be a loser because some people would still like that. There's such a pressure to be a winner in America – it's so stifling and claustrophobic.'

In Unhappy Birthday Lamé explores the notion of über-fandom and how it can define key moments in our lives. She invites the audience – and Morrissey – to her party for pass-the-parcel and an emotional unravelling, compounded by the non-appearance of the VIP guest.

'It's Waiting for Godot for the pop generation,' says Lamé. 'It's a love/hate thing with Morrissey. Love me, hate me, I don't care. He's never fully answered certain questions: about his sexuality, about why he moved to LA. He'll give a little bit but keep something hidden so you're always compelled to keep searching. When it comes to being a Morrissey fan it's not as easy as liking some fluffy pop puppet, and that's part of the attraction.'

Whatever the allure, he is the ideal vessel for über-fandom: the movie idol looks that, if anything, have improved with age; the dark, complex lyrics; the obfuscation of details about his personal life; the controversial interviews. Even when his fans don't agree with him – and they often don't – many defend him on the ground he's misunderstood, throwing apoplectic cyber-tantrums to make a point. Morrissey, to his credit, repays the adulation, graciously accepting the presents that come his way, dispensing hugs, inviting stage invasions and mingling with autograph hunters. He is a fan himself: in the late 1970s he co-founded The Legion of the Cramped, a fan club celebrating the musical output of cult American garage punk band The Cramps. At the heart of it all, of course, is a musical output that captures the essence of what it feels like to be an outsider. See also Marc Almond, Freddie Mercury and, more recently, Lady Gaga.

Kirstyn Smith, 26, a researcher from Edinburgh, agrees: 'He says it's OK to embrace the darker side of reality, to embrace your flaws. It's OK to be an outsider.' Smith has been a Morrissey fan since she was a teenager. When he tours the UK she buys tickets for as many of the dates as she can 'reasonably afford' and is saving to go to gigs in the US later in the year. She has a tattoo of his autograph on her arm, obtained after meeting him after a gig a few years ago. But she objects to the image of the Morrissey fan as a slavish devotee.

'Nearly everybody has something [they are obsessed with],' she says. 'But it's probably more socially acceptable to be a football fan. I've always been wary of the way I'm perceived – it feels like you have to fight against the stereotype of depressed, crazy person. I know there's a sort of sense that if you're a big fan of somebody, particularly somebody as controversial as Morrissey, you must agree with everything he says. Obviously, this is nonsense.'

Smith has made some good friends at Morrissey gigs. The same is true for Robert Winning, the founder of Morrissey and The Smiths night Strangeways, which takes place several times a year in Glasgow and Edinburgh. 'I plan my whole life around Morrissey gigs,' he says, only half joking. 'The Morrissey fan community is very close-knit, even though they come from all over. I've had people come [to Strangeways] from London and Ireland – we even had someone from Brazil. He's still relevant and that's why a younger generation is discovering his music.'

Old and new, Morrissey fans go that extra mile for their idol. A quick survey in the pub unearths stories of men who have left their wives, a woman who gave up her job to follow one of his European tours and a former flatmate who played 'The More You Ignore Me, the Closer I Get' five times every night before going to bed for 18 months.

But what makes a fan, whether mad or measured? Author and cultural commentator Allan Brown – who has written several books that attest to his own attention to obsessive detail – believes it's a fate reserved for only the most romantic among us.

'True obsessives fixate either on messianic individuals (Lennon, Bowie, Morrissey; the only ones wise enough to understand the obsessives' complex, unique thoughts) or on periods of time (my own obsession, or Noel Gallagher's, with the 1960s).

'Obsessives know in their hearts that their needs are wretched but they can't help themselves; they want simply to appear in the cosmic Super-8 movie of the thing they love. They want to possess something that comes from what they believe to be a better, happier, more wholesome time or to touch the hem of an individual they believe to be blessed.

'All this is true, I think, of Morrissey, whose real obsessive constituency would be 40-year-olds who got laid to his records at college, or 25-year-olds who can't visualise a world so golden as to contain him at his peak.'

Unhappy Birthday, Assembly 3, George Square, 2-26 Aug; Half a Person: My Life as Told by The Smiths, Zoo Southside, 3-27 Aug; Strangeways returns in Sep.

TOTP - This Charming Man - The Smiths