He's as mad as hell and isn't going to take it anymore - and there are a lot more 'bus uncles' lurking out there, according to psychologists. The cult video of the six-minute tirade unleashed by a middle-aged traveller on unsuspecting young 'Alvin' has become an internet classic, downloaded by millions not only in Hong Kong but around the world. The vengeful Bus Uncle tirade has also spawned a line of merchandise - including underwear, mugs and rucksacks carrying his trademark phrase: 'I've got pressure!' The video of Bus Uncle exploding, after being tapped on the shoulder by Alvin and told to tone it down while speaking on a mobile phone, has inspired six different versions, including karaoke and music videos, and fake newscasts. His words: 'You've got pressure! I've got pressure! Why are you provoking me?' and 'It's not over! It's not over! It's not over!' have been turned into mobile ring tones and become the latest catchphrases. As funny as some people find the video, medical and cultural experts say it is no laughing matter because Hong Kong is teeming with 'bus uncles' waiting to explode. 'Hong Kong's macroclimate is that everyone feels annoyed all the time and angry some of the time,' said Lee Sing, director of the Hong Kong Mood Centre at the Chinese University. 'People get yelled at by their boss or have a fight with their spouse but cannot yell back so they feel stress, anxiety and depression. The whole Bus Uncle phenomenon shows that society has reached a tipping point.' Dr Lee says one out of every 50 grumpy people in Hong Kong is a ticking time bomb when it comes to rage. He believes Bus Uncle is a classic example of someone with Intermittent Explosive Disorder (IED) or full-time road rage. Bus Uncle, like IED sufferers, tried to resolve the conflict - in this case by asking for an apology and offering to shake hands - but could not stop himself from continuing to be angry. 'When such a small thing triggers such a prolonged angry response, the person must have a problem. They cannot stop themselves even if they want to,' Dr Lee said. Pop culture and internet expert Anthony Fung Ying-him agreed, saying the general emotional climate helped catapult a low-quality video capturing a trivial event to celebrity status. 'Internet videos like this one used to be popular with very specific groups of people but this one transcended the barriers because the social issue is so universal,' he said. According to the Diagnostic and Statistical Manual of Mental Disorders, IED is like male premenstrual tension and is characterised by specific episodes of violent and aggressive behaviour which are grossly out of proportion to the situation. Dr Lee suggests that people who have doubts about their ability to control their rage should seek professional help.