Half of all those taking antidepressants experience withdrawal problems when they try to give them up and for millions of people in England, these are severe, according to a new review of the evidence commissioned by MPs.

Guidance from the National Institute of Health and Care Excellence (Nice), which says withdrawal symptoms “are usually mild and self-limiting over about one week” urgently needs to be changed, say the review authors.

Dr James Davies from the University of Roehampton and Prof John Read from the University of East London say the high rate of withdrawal symptoms may be part of the reason people are staying on the pills for longer. They cannot cope, so carry on taking the drugs, or their doctors assume they have relapsed and write another prescription.

The review was commissioned by the all-party parliamentary group for prescribed drug dependence and follows a long debate about the Nice guidance, which critics say is out of date.

Modern antidepressants of the SSRI class, such as Prozac (fluoxetine) and Seroxat (paroxetine), were marketed in part on their safety. Studies showed that when taken alone, overdoses were rarely fatal, which was not the case with benzodiazepines. Also, stopping the drugs was said to be easier.

This new review of the research reveals what many patients have known for years Dr James Davies

There have been plenty of anecdotal accounts of withdrawal symptoms, which include dizziness, vertigo, nausea, insomnia, headaches, tiredness and difficulties concentrating. But the Nice guidance said in 2004 that the withdrawal symptoms were slight and short-lived and was re-adopted without further evidence in 2009. It is similar to the US guidance, which says symptoms usually resolve within one to two weeks.

The review, published in the journal Addictive Behaviors, focused on 14 studies of antidepressants that had relevant data on withdrawal symptoms. The studies, which were diverse, showed that between 27% and 86% of people suffered from them, with a weighted average of 56%.

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Antidepressants are now some of the most commonly prescribed drugs in the UK and US, say the authors. “In the UK, usage has risen since 2000 by 170%, with over seven million adults (16% of the English adult population) being prescribed an antidepressant in England alone last year,” says the review.

About half of antidepressant users have been taking the pills for longer than two years. In England, that is 3.5 million people – 8% of the population. In the US, 13% of the population (37 million adults) were on them by 2011-2014, official data shows. Half have been taking them for five years or more.

“This new review of the research reveals what many patients have known for years – that withdrawal from antidepressants often causes severe, debilitating symptoms which can last for weeks, months or longer,” said Dr James Davies.

“Existing Nice guidelines fail to acknowledge how common withdrawal is and wrongly suggest that it usually resolves within one week. This leads many doctors to misdiagnose withdrawal symptoms, often as relapse, resulting in much unnecessary and harmful long-term prescribing.”

In addition to updating the existing evidence reviews, we will include new work on patient choice Nice

The review includes comments from some of the studies where antidepressant users were interviewed about their experiences of trying to wean themselves off the pills.

One spoke of “horrible dizzy spells and nausea whenever I lower my dose”. Another said: “The withdrawal effects if I forget to take my pill are severe shakes, suicidal thoughts, a feeling of too much caffeine in my brain, electric shocks, hallucinations, insane mood swings … kinda stuck on them now coz I’m too scared to come off it.”

Sir Oliver Letwin MP, chair of the parliamentary group, said: “This systematic review provides important new data on antidepressant withdrawal which will be considered by Public Health England as part of their current review into prescribed drug dependence. The data suggests that existing medical guidelines in this area should be urgently updated to reflect the fact that antidepressant withdrawal is much more common, severe and long-lasting than previously stated. Furthermore, we hope that other medical bodies will take note of this new research, and update their own guidance accordingly.”

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Nice said it is looking again at its guidance. “In July 2018, the committee met and concluded that the current evidence base needs updating to include research from July 2016 onwards. Nice agrees,” said Paul Chrisp, director of the Centre for Guidelines at Nice. “It is important that the final recommendations are based on the most up-to-date evidence possible. In addition to updating the existing evidence reviews, we will include new work on patient choice and a focus on shared decision making.

“We hope the final guideline will allow people with depression to be offered the best treatments and reach joint decisions about their care that reflect their preferences and values.”

• This article was amended on 3 October 2018 to clarify how overdosing on SSRI antidepressants differs from overdosing on benzodiazepines.