One out of every six people have symptoms when they stop taking antidepressants – fewer than previously thought, a review of previous studies suggests.

The researchers say their findings will help inform doctors and patients “without causing undue alarm”.

The Lancet Psychiatry review looked at data from 79 trials involving more than 20,000 patients.

Some had been treated with antidepressants and others with a dummy drug or placebo, which helped researchers gauge the true effect of withdrawing from the drugs.

Some people have unpleasant symptoms such as dizziness, headache, nausea and insomnia when they stop taking antidepressants, which, the researchers say, can cause considerable distress.

Previous estimates suggested antidepressant discontinuation symptoms (ADS) affected 56% of patients, with almost half of cases classed as severe.

But this review, from the Universities of Berlin and Cologne, estimates:

• One out of every every six or seven patients can expect symptoms when stopping antidepressants
• One in 35 will have severe symptoms
• Symptoms are more common with some antidepressants than others

Official health guidance is to reduce the dose of antidepressant medication in stages over time, rather than stopping it suddenly or missing doses, which could lead to withdrawal symptoms.

Most people stop antidepressants successfully, the guidance adds.

Other research suggests ADS lasts for one to two weeks.

Study author Prof Christopher Baethge, from the department of psychiatry and psychotherapy, at the University of Cologne, said the findings were “quite robust”.

But the review’s lower estimate of ADS “did not mean it’s all in their heads”.

It found 17% of people experienced symptoms after stopping a placebo or dummy drug.

“A possible explanation is greater awareness of worsening anxiety and depression after stopping a seemingly helpful medication,” Prof Baethge said.

Many of the 40 symptoms linked to stopping antidepressants can also be caused by other ailments.

“It shows the importance of comparing antidepressants with placebo when studying discontinuation,” said Prof Glyn Lewis, from University College London.

The most commonly used antidepressants in the UK – citalopram, sertraline and fluoxetine – had the lowest risk of ADS.

But venlafaxine, which is also used in the UK, had the second highest.

Consultant psychiatrist and fellow of the Royal College of Psychiatrists Dr Paul Keedwell said people planning to stop their medication should always seek medical advice.

“Firstly, depending on your mental-health history, there might be a high risk of relapse of your depression,” he said.

“Sometimes a relapse of depression can be confused with withdrawal symptoms.

“Secondly, unpleasant withdrawal symptoms can be largely prevented with proper medical supervision.

“It is important to say that withdrawal symptoms are not dangerous and the risk of experiencing them at some future date should not be a reason for refusing antidepressant treatment.

“The pros and cons of treatment should always be discussed with your doctor.”

More than eight million people in England are taking antidepressants, for depression, anxiety, obsessive-compulsive disorder and other conditions – a million more than five years ago.