What are antidepressants? 

Antidepressants are psychiatric drugs which are licensed to treat depression. Some are also licensed  to treat other conditions, such as: 

  • anxiety disorders 
  • phobias 
  • bulimia (an eating disorder)
  • some physical conditions, including managing long-term pain.

Who can prescribe antidepressants? 

The healthcare professionals who can prescribe you antidepressants include:

  • a psychiatrist 
  • your family doctor 

Many antidepressants can be prescribed by your doctor, although some may only be prescribed if you are supervised by a mental health professional, such as a psychiatrist. 

These information pages refer to ‘your doctor’ prescribing medication, as they are the most likely person to prescribe you an antidepressant. 

“I took medication for six months. It helped lift the fog and gave me the energy I needed to tackle the  root cause of my depression. There is no shame in taking medication to treat an illness.” 

How do antidepressants work?

Antidepressants can treat the symptoms of depression or other mental health problems. But they don’t always deal with the causes. Doctors will often prescribe them alongside a talking therapy, to help deal with the causes of your mental health problems. 

You may find that some types of antidepressant work better than others for your symptoms. Or you may find that antidepressants aren’t right for you. See our page on how antidepressants can help to find out more. 

What’s the science behind antidepressants? 

Antidepressants work by boosting the activity of particular brain chemicals, or making its activity last longer. This includes noradrenaline and serotonin, which are thought to be involved in regulating your mood.

Noradrenaline and serotonin are neurotransmitters. This means that they are chemicals which function to pass messages between nerve cells in your brain, and between nerves and other organs in the rest of your body. 

By causing a change to your brain chemistry, antidepressants may lift your mood. But antidepressants don’t work for everyone. And there is no scientific evidence that depression is caused by a chemical imbalance which is corrected by antidepressants. 

What different types of antidepressant are there? 

There are several different types of antidepressant. They mostly affect the same brain chemicals and cause similar effects. But some people may respond to certain antidepressants better than others. And the different drugs may cause different side effects. 

The different types are: 

  • selective serotonin reuptake inhibitors (SSRIs) 
  • serotonin and noradrenaline reuptake inhibitors (SNRIs) 
  • tricyclics and tricyclic-related drugs 
  • monoamine oxidase inhibitors (MAOIs) 
  • other antidepressants 

Selective serotonin reuptake inhibitors (SSRIs) 

About SSRIs: 

  • SSRIs mainly work by blocking the reuptake of serotonin into the nerve cell that released it.  This means that the serotonin acts for longer on your brain and body. 
  • You may find the side effects of SSRIs easier to cope with than with other antidepressants. But these effects can still feel unpleasant, especially when you first start taking the drugs. 
  • SSRIs are the most commonly prescribed type of antidepressant in Hong Kong. 

Serotonin and noradrenaline reuptake inhibitors (SNRIs) 

About SNRIs: 

  • SNRIs work in a similar way to SSRIs. But they also have a significant effect on your noradrenaline reuptake. 
  • Like SSRIs, you may find that you can take SNRIs without experiencing too many unwanted side effects. But their side effects can still be unpleasant.
  • SNRIs are sometimes preferred for treating more severe depression and anxiety.

Tricyclics and tricyclic-related drugs 

About tricyclics: 

  • Like SNRIs, tricyclics affect your reuptake of noradrenaline and serotonin, making their effects on your brain and body last longer. 
  • But tricyclics also affect some other chemicals in your body. This can mean they’re more likely to cause unpleasant side effects than other antidepressants. 
  • They’re called ‘tricyclic’ because of their chemical structure, which has three rings. About tricyclic-related drugs: 
  • These act in a very similar way to tricyclics, but they have a slightly different chemical structure. 
  • Tricyclic-related drugs tend to cause more unpleasant side effects compared with other types of antidepressants, such as SSRIs or SNRIs. But they are less likely to cause antimuscarinic side effects than tricyclics.

Monoamine oxidase inhibitors (MAOIs) 

About MAOIs: 

  • MAOIs work by making it harder for an enzyme called monoamine oxidase to break down noradrenaline and serotonin. This causes noradrenaline and serotonin to stay active for longer in your brain and body. 
  • MAOIs can have dangerous interactions with some kinds of medication and food. If you take  MAOIs, you need to follow a careful diet. And you should always check with a doctor or pharmacist before taking any new medication alongside MAOIs. 
  • MAOIs should only be prescribed by a specialist. You are unlikely to be prescribed an MAOI  unless you’ve tried all other types of antidepressant, and none of them have worked for you.  This is because of the dangerous interactions that are possible with MAOIs. 

Other antidepressants 

There are several other antidepressants available which don’t fit into any of the categories above.  


Next page