Are antidepressants addictive?

12 May 2018

Antidepressants have long been surrounded by controversy: are too many people taking them? Or are doctors too reluctant to prescribe them? Do they even work? And might they even be considered to be addictive?

A recent review article published in the Lancet, one of the leading medical journals, has concluded that antidepressants are more effective than placebo in treating adults with depression. The authors argued that this information should be used to inform medical guidelines and recommendations for treatment going forward.

However, the effectiveness or otherwise of antidepressants is only one side of the story. Another major concern expressed by both patients and doctors is with regard to the longer-term effects of antidepressant use. Specifically, there are questions surrounding what happens when patients stop taking antidepressants. It is well known that some people experience a number of unpleasant symptoms when they discontinue their medication, particularly if they stop abruptly. But does this mean that antidepressants are addictive?

What is addiction?

Addiction is a "popular" concept, with the term being applied indiscriminately to describe anything from consuming strong opioids to smartphone overuse. However, "addiction" does have an official psychiatric definition. This is based around a cluster of symptoms which together constitute "dependence syndrome". The features of dependence syndrome map quite closely onto what most of us would recognise as the behaviour of a person who is addicted. But when we're trying to work out whether or not something has the potential to be addictive, it is useful to be able to formalise what we know to be somewhat intuitively true. The "dependence syndrome" framework for understanding addiction works very well in terms of describing abuse of substances such as street drugs, alcohol, and prescription medications; it works less well for describing "addiction" to more nebulous entities such as Internet usage. In any case, since antidepressants are quite straightforwardly a "substance", this set of criteria can be applied to their use.

The key feature of dependence syndrome is a sense of craving - a strong compulsion to take the substance in question. Further to this, the addicted individual has trouble regulating how they use the substance - they cannot control when they use the substance, how often they take it, or indeed, how much they take at a time. As a result, they begin to neglect other activities and interests, as their substance use occupies an increasing portion of their day. However, despite the clear harm the substance is causing them, be that physical, psychological or social, the addicted person continues to seek it out, finding it very hard to stop using it. Importantly, in dependence disorder, there is often also evidence that the substance is directly affecting the addict’s brain biochemistry: with time and use, progressively higher doses of the substance are required to give the same "hit". This is known as tolerance. Finally, should the individual not be able to secure a sufficiently high dose of the addictive substance, they experience a set of physical symptoms called "withdrawal", which tend to be characteristic to the addictive substance: someone withdrawing from alcohol will look very different to someone withdrawing from heroin - but all withdrawing alcoholics will show virtually identical symptoms.

So, what happens when we apply this framework of dependence syndrome to antidepressant use?

Antidepressant discontinuation syndrome

The main argument used in favour of antidepressants being regarded as addictive is that, upon stopping these medications, people often experience a discontinuation ("withdrawal") syndrome. This syndrome is universally and uncontroversially recognised.

Whether or not someone experiences the symptoms of discontinuation syndrome depends on a number of factors: Firstly, antidepressants are not all the same - they consist of several distinct drug categories. It is recognised that some categories of antidepressants are much more likely than others to produce a discontinuation syndrome. Additionally, antidepressants vary in how long they stay in the body for. Those which leave the body more quickly (in other words, have a shorter half life) are more likely to produce such symptoms, occasionally even when a single dose is missed. Finally, discontinuation syndrome is more likely to occur when antidepressants are stopped abruptly, rather than the dose being tapered down over a matter of days.

This means that discontinuation syndrome does not affect all users of antidepressants, but those who do suffer from it tend to experience similar symptoms: they usually feel run down, similar to having the flu. They can also experience insomnia, sometimes with very vivid dreams on falling asleep. On the more severe, and generally more rare, end of the spectrum, some may find that their memory and concentration is worse than usual, and in extreme cases, a person’s mental health may be affected, with irritability, episodes of tearfulness and crying, and even mania (feelings of excitement of euphoria, often accompanied by hyperactivity).

This may all sound quite concerning - but according to the Royal College of Psychiatrists, symptoms do not occur in the vast majority of cases, and when they do, they are usually mild, and tend to subside within a couple of weeks. Furthermore, if discontinuation syndrome occurs, re-starting the antidepressant and cutting it down more slowly is usually effective in resolving the symptoms.

Is this addiction?

Does this discontinuation syndrome map on to our earlier definition of addiction? Experiencing withdrawal is certainly one of the components of dependency. However, in order to formally diagnose "dependence syndrome", a person generally needs to have exhibited three or more of its characteristic symptoms or behaviours. So is there any evidence that users of antidepressants show any other features consistent with addiction?

As it happens, people on antidepressants do have trouble stopping them. However, this is not due to a compulsion to continue taking the medication. Usually, patients are simply anxious about stopping, worrying that their depression will recur. Another concern that comes up in studies is that patients believe that the medication they are on might be addictive - perhaps having heard about discontinuation syndrome - and therefore they fear the effects stopping the medication might have on them. A slight subtlety is that in order to classify as addiction, continued use of the substance must be in the context of persistent negative effects stemming from this use. In the case of antidepressants, people generally continue taking them because of overwhelmingly positive effects. As such despite the difficulty some people experience when trying to come off antidepressants, this cannot really be seen as a feature of dependence syndrome.

In terms of the other features of addiction, there is no evidence that antidepressant users crave their antidepressants, or have any difficulty in controlling how much of their antidepressant they use. Furthermore, for most people, their antidepressant use will not interfere with their pursuit of other interests and interpersonal relationships - if anything, the effect is quite the opposite. Finally, even though occasionally users may have to increase their antidepressant dose in order to achieve good control of their depression symptoms, there is no evidence that this is due to "tolerance". In addictive substances, tolerance is generally associated with biochemical change at the level of the brain and the wiring of its neurons. In antidepressant use, even though there may be some such changes, the patterns of re-wiring that occur would not be expected to produce tolerance. This is partly because addictive substances and antidepressants affect different pathways within the brain: drugs of abuse tend to affect the brain’s reward systems, which are based on nerve cells which communicate through the molecule dopamine. By contrast, most antidepressants tend to affect pathways which are based on other molecules, such as serotonin (the "happiness molecule" in the brain).

There is also some evidence from animal studies that antidepressants are unlikely to be truly addictive: when animals are given access to drugs that are addictive to humans, they tend to very quickly learn to self-administer them, for instance through pressing a button which results in a dose injection. However, no such effect is observed with antidepressants.

The verdict

The vast majority of evidence appears to indicate that antidepressants are probably not addictive. However, this does not change the fact that some antidepressant users in studies self-report as being "addicted" to their medication (even in the absence of any obvious signs of addiction). This may to a certain extent reflect the lack of education from doctors to patients regarding antidepressant discontinuation syndrome - studies show that this is something that is not generally discussed in consultations when antidepressants are prescribed. As such, it is possible that some people interpret their discontinuation symptoms as arising from addiction. However, it is still possible that this explanation may not account entirely for this effect: there exists a small subgroup of people who seem to experience very real addiction on antidepressants. These cases are few and far between, and tend to involve categories of antidepressants that are very rarely used, or which have been unlicensed for use for many years. This makes these instances of addiction easy to dismiss. However, as we still know relatively little about exactly how antidepressants work in the brain, it is probably wise to keep an open mind.

If you are taking antidepressants and you have any queries or concerns about your medication, your GP can provide you with more information. In the UK, the Samaritans can be reached on 116 123. International suicide helplines can be found at www.befrienders.org

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