Taking antidepressants for more than two years is associated with a higher risk of withdrawal symptoms compared to short-term use, UK researchers have found.
The team from University College London (UCL) found that those who have been taking antidepressants for longer also tend to experience worse withdrawal symptoms, over a longer period and are less likely to be able to successfully stop taking them.
The findings come from a survey of 310 participants in England using NHS primary care therapy services who had at one point tried to stop taking their prescribed antidepressant.
Most participants – 62% – found that antidepressants had been helpful, the researchers reported in Psychiatry Research.
In all, 79% reported at least one withdrawal symptom with 30% citing symptoms they classified as moderate and 15% said symptoms were severe.
Among the participants, 38% said they were unable to stop antidepressants when they tried to do so, rising to 79% among people who had been taking antidepressants for two years or more.
The odds of experiencing any withdrawal effects were 10 times greater with antidepressant use of more than two years, compared to less than six months, the researchers said.
Among those who had been taking antidepressants for two years of more, 64% reported moderate or severe withdrawal effects; and 73% reported either no withdrawal effects or only mild symptoms when they had been taking them for less than six months.
For long-term users, 30% reported withdrawal symptoms lasting more than three months, with 12% experiencing such symptoms for more than a year.
This compared with 10.5% of short-term users experiencing withdrawal symptoms for more than three months. In most cases in this group withdrawal symptoms resolved in under four weeks.
Some symptoms, such as anxiety, worsened mood, agitation and fatigue overlap with depression and anxiety, the researchers said, but 76% of respondents experienced at least one non-emotional withdrawal symptom such as dizziness, headache, vertigo, or nausea.
The differences between short-term and long-term users were not explained by the severity of the underlying depression or anxiety disorder.
Lead author Dr Mark Horowitz, visiting clinical researcher at UCL Division of Psychiatry, said: ‘Our findings confirm what many researchers have long suspected, that the likelihood of experiencing withdrawal symptoms when coming off antidepressants is largely determined by duration of use.
‘While coming off antidepressants can be easier for people who have only taken them for a short period of time, these drugs are commonly used for a long time.
‘Half of those in the UK who take antidepressants have taken the medication for at least a year, and the majority of US antidepressants users have been taking them for over two years.’
The survey was not only about withdrawal, but it is possible that those who had symptoms when they tried to stop were more motivated to answer the survey.
A study published last year found that GPs could support almost half of patients taking long-term antidepressants to safely come off the drugs as long as they were well and willing to stop.
In 2022, NICE concluded that antidepressants are not ‘dependence-forming’ drugs, although they can cause withdrawal symptoms.
NICE also recommended that GPs should provide regular reviews for patients on antidepressants and drugs for chronic pain that may cause dependency or withdrawal.
Professor Anthony Kendrick, professor of primary care at the University of Southampton, said the number of people in the survey reporting severe withdrawal symptoms is likely to be an overestimate due to the design of the research.
He said: ‘Overall we might conclude that the evidence so far indicates that a minority of people experience severe withdrawal symptoms – somewhere between 3% and 15%.’
