No self-respecting manager would be without a BlackBerry. But now these handheld gadgets, which provide workaholics with constant email updates, are being blamed for chronic insomnia, relationship break-up, premature burn-out, and even car crashes. British employers are being warned they could face multi-million-pound legal actions from BlackBerry-addicted staff on a similar scale as class law-suits taken against tobacco companies.
Research by the University of Northampton has revealed that one-third of BlackBerry users showed signs of addictive behaviour similar to an alcoholic being unable to pass a pub without a drink.
The report found that some BlackBerry users displayed textbook addictive symptoms - denial, withdrawal and antisocial behaviour - and that time with their families was being taken up with BlackBerry-checking, even at the dinner table.
Professor Nada Kakabadse, joint author of the study, said that lawsuits were a growing issue for employers who were being sued for failing in their duty of care to staff and in following health and safety guidelines. In one case in the US, a female business consultant claimed that her marriage fell apart because she was constantly checking messages. She ended up losing custody of her children and sued her employer for damages.
"Enlightened companies that issue BlackBerrys as standard like pen and paper should also have policies on how to use them, so that people can use technology in a way that doesn't have an addictive side," said Professor Kakabadse of Northampton Business School.
The BlackBerry backlash has already begun in the US, where firms are settling out of court to avoid negative publicity.
The Independent on Sunday has learnt that, in one recent case, an employer had to pay substantial damages to a woman who was so distracted by her BlackBerry while driving that she crashed and killed a motorcyclist. In another, a woman took action after putting cleaning fluid on her baby's nappy instead of baby oil because she was distracted by her BlackBerry.
And last week, health officials warned of a painful new syndrome - BlackBerry Thumb - caused by excessive use of the portable devices. The American Physical Therapy Association says that middle-aged businessmen are particularly at risk of this disorder, which can aggravate arthritis.
More than five million BlackBerrys have been sold worldwide since they were first launched eight years ago and they have been credited with revolutionising working life. Also known as personal data assistants, these palm-sized handsets allow people to send and receive emails and other messages as well as to browse the internet.
The maker of BlackBerry, Research In Motion, argues that the machines enable people to be more efficient and to save "dead" time while in transit or waiting for meetings. However, experts are increasingly warning that they are as addictive as drugs and alcohol. They have even been dubbed "crackberries" because some users say they make them feel compelled to check messages constantly.
This comes as a new study reveals that nine out of every 10 users have a compulsive need to check for messages and that nearly half experience long-term negative consequences associated with carrying a BlackBerry. A survey of business workers by researchers at the Sloan School of Management at Massachusetts Institute of Technology in the US found that employees were constantly tired because they were waking up in the middle of the night to check or send messages. One interviewee likened the sense of potential gain from staying in touch with work to "pulling the lever of a slot machine".
Melissa Mazmanian, one of the report's authors, described the BlackBerry as a "comfort blanket", which fulfils the human need to reach out to others but also maintains a sense of control, unlike a telephone conversation. "Spouses find it frustrating and aggravating and to avoid problems couples have to negotiate rules and boundaries over use," said Ms Mazmanian.
Her findings are backed up by an investigation carried out by the Chartered Management Institute. This found that managers are now under extreme pressure to be contactable around the clock, but this has a hugely negative impact on productivity, health and wellbeing. This is exacerbated by the fact that many take communication gadgets, such as Blackberrys, laptops and mobile phones, away on holiday and refuse to switch them off.
Phillip Hodson, from the British Association for Counselling and Psychotherapy (BACP), said that devices such as BlackBerrys were "beguilingly seductive" because they provide the illusion of freeing up more time, but that the human brain was not properly adapted to the multi-tasking that modern life demands. "The real battle now is not over money but over who controls time," he said. "What this nation needs is eight hours' work, eight hours' rest and eight hours' play a day. Gordon Brown doesn't know how to play, that's his problem - he's probably on his BlackBerry."
The Chartered Institute of Personnel and Development (CIPD) said that employers should actively discourage office cultures where people feel they are under pressure to be working round the clock.
But Martyn Sloman, policy adviser to the CIPD, said that people do need to take responsibility for their own behaviour rather than "shooting the messenger".
A spokesman for the manufacturers of BlackBerry dismissed suggestions that the machines are addictive. "They reclaim that productive time each day that would otherwise be wasted in transit or waiting for meetings," said James Hart, vice-president of Research In Motion. "BlackBerry handsets can help us to achieve more - both at work and at home. But, as with any piece of technology, the most important button is the 'off' switch."