The side effects of antidepressants can cause problems at first, but then generally improve with time.
It's important to continue treatment, even if you're affected by side effects, as it will take several weeks before you begin to benefit from treatment. With time, you should find that the benefits of treatment outweigh any problems from side effects.
During the first few months of treatment, you'll usually see your doctor or a specialist nurse at least once every two to four weeks to see how well the medication is working.
Some of the more common side effects of the main types of antidepressants are outlined below. For more information about your specific medication, see the patient information leaflet that comes with it.
SSRIs and SNRIs
Common side effects of selective serotonin reuptake inhibitors (SSRIs) and serotonin-noradrenaline reuptake inhibitors (SNRIs) can include:
These side effects should improve within a few weeks, although some can occasionally persist.
Tricyclic antidepressants (TCAs)
Common side effects of TCAs can include:
The side effects should ease after a couple of weeks as your body begins to get used to the medication.
Potential health risks
Serotonin syndrome is an uncommon, but potentially serious, set of side effects linked to SSRIs and SNRIs.
Serotonin syndrome occurs when the levels of a chemical called serotonin in your brain become too high. It's usually triggered when you take an SSRI or SNRI in combination with another medication (or substance) that also raises serotonin levels, such as another antidepressant or St John’s Wort.
Symptoms of serotonin syndrome can include:
- muscle twitching
If you experience the symptoms listed above, you should stop taking the medication and seek immediate advice from your GP or specialist. If this isn't possible, call NHS 111.
Symptoms of severe serotonin syndrome include:
- a very high temperature (fever)
- seizures (fits)
- irregular heartbeat (arrhythmia)
If you experience symptoms of severe serotonin syndrome, seek emergency medical help immediately by dialling 999 to ask for an ambulance.
Elderly people who take antidepressants, particularly those who take SSRIs, may experience a severe fall in sodium (salt) levels, known as hyponatraemia. This may lead to a build-up of fluid inside the cells of the body, which can be potentially dangerous.
This can happen because SSRIs can block the effects of a hormone that regulates levels of sodium and fluid in the body. Elderly people are vulnerable because fluid levels become more difficult for the body to regulate as people age.
Mild hyponatraemia can cause symptoms similar to depression or side effects of antidepressants, such as:
- feeling sick
- muscle pain
- reduced appetite
More severe hyponatraemia can cause the following symptoms:
- feeling listless and tired
- seizures (fits)
The most serious cases of hyponatraemia can cause you to stop breathing or enter a coma.
If you suspect mild hyponatraemia, you should call your GP for advice and stop taking SSRIs for the time being.
If you suspect severe hyponatraemia, call 999 and ask for an ambulance.
Hyponatraemia can be treated by feeding a sodium solution into the body through an intravenous drip.
Long-term use of SSRIs and TCAs has been linked to an increased risk of developing type 2 diabetes, although it's not clear if the use of these antidepressants causes diabetes to develop directly.
It may be that the weight gain some people using antidepressants experience increases the risk of them developing type 2 diabetes.
For more information, see "Claim that antidepressants cause diabetes unproven".
In rare cases, some people experience suicidal thoughts and a desire to self-harm when they first take antidepressants. Young people under 25 seem particularly at risk.
Contact your GP, or go to hospital immediately, if you have thoughts of killing or harming yourself at any time while taking antidepressants.
It may be useful to tell a relative or close friend if you've started taking antidepressants and ask them to read the leaflet that comes with your medication. You should then ask them to tell you if they think your symptoms are getting worse, or if they're worried about changes in your behaviour.