Antidepressants are types of medication used to treat clinical depression. However, the name is also somewhat misleading, as many antidepressants are also prescribed for a range of other disorders. These include other mental health problems such as anxiety, obsessive-compulsive and post-traumatic stress disorders; they may also be used to treat conditions like long-term pain.
How do they work?
It is not fully clear how antidepressants produce their effects as we still do not fully understand depression, but it is thought that it is due at least in part, to increasing levels of neurotransmitters such as serotonin and noradrenaline. Such neurotransmitters have a role in improving mood and protecting against stress, though as with many aspects of neuroscience this is not completely understood.
Different types of antidepressants
There are a number of different types of antidepressant drugs of which the newer selective serotonin reuptake inhibitors (SSRIs e.g. fluoxetine, sertraline, paroxetine, citalopram) are the most commonly used and are generally the first choice for treatment for the conditions listed above. Newer antidepressants are used because they have better tolerated side effects and are safer in overdose than the old ones (see below); however effectiveness of both is similar.
Other antidepressants include serotonin-noradrenaline reuptake inhibitors (SNRIs e.g. venlafaxine & duloxetine), noradrenaline and specific serotonergic antidepressants (NASSAs) and tricyclic antidepressants (TCAs). TCAs are often reserved for use in cases of severe depression or OCD, and aren’t used as a first-line treatment because they are associated with more unpleasant side effects and a greater risk of overdose.
What are the side effects?
Side effects can vary between the different classes but can include nausea, loss of appetite or sexual dysfunction with SSRIs, and drowsiness or weight gain with TCAs.
Depression in pregnancy and following childbirth can potentially have serious consequences; suicide is a leading cause of maternal death in the UK. Recent research suggests that whilst the absolute risk of birth defects remains very low, there is an increased risk following the use of anti-depressants during the first three months of pregnancy. There is debate about whether the defects are caused by the medication, or the illness itself. RCOG states that their advice for pregnant women suffering with depression is that the benefits of using antidepressants generally outweigh the risks, however all pros and cons should be discussed with a clinician.
How effective are they?
Most antidepressants won’t work immediately but their effects can be felt after around one or two weeks though this is variable. The lowest possible dose is usually prescribed to reduce the risk of side effects. If only minimal benefit is felt after one month then an increase in dose may be recommended, and if no benefit is seen then a change in medication may be recommended. A course will typically last for at least six months.
Estimates of effectiveness suggest 50-65% of patients treated for depression with an antidepressant benefit compared with around half that figure for people who are treated with a placebo.
Many organisations suggest that the prescription of antidepressants should be avoided in children below the age of 12 as efficacy is lower in this group. It is recommended that people under the age of 18 receive psychotherapy first, though a specific antidepressant (fluoxetine/Prozac) may be used as a first option in non-responsive cases or cases of moderate/severe depression (Sertraline/Citalopram as a second option).
How commonly are they prescribed?
Antidepressants are usually a first line of treatment in adults with moderate to severe depression and the first line treatment given to people with anxiety disorders.
Antidepressant prescription is common and may be increasing. There is a lot of interest in both possible over – and under – prescribing of antidepressants.
A recent report stated that the prescription of antidepressant drugs in England saw a significant rise between 1998 and 2012.
Coupled with this, access to specialist knowledge and care is not always well integrated with primary care which can further lead to misdiagnosis or wrongful prescription.
A common perception is that patients should stop taking antidepressants as soon as possible, but for some patients (particularly those who have recurrent episodes) they may need to consistently take the drugs over the long term (i.e. years) to prevent relapses. There is good evidence that antidepressants should be taken for a full 6 months after recovery for first episodes of depression and longer after recurrent episodes.
This is a Factsheet issued by the Science Media Centre to provide background information on science topics relevant to breaking news stories. This is not intended as the ‘last word’ on a subject, but rather a summary of the basics and a pointer towards sources of more detailed information. These can be read as supplements to our Roundups and/or briefings.