The Science behind Antidepressants

Antidepressants and other pills

Trigger warning: This article discusses depression and suicidal thoughts.

There are lots of different drugs used to treat mental health conditions, and you may have (like I was several years ago) been handed a prescription and had literally no idea what the drug was or what it would do. So if — like me — you want to know a little more about the medication you are (or are thinking about) taking, here’s some information about how anti-depressants work to help you out.

If you are taking a medication and don’t know what it does and you have any concerns, please speak to your GP or pharmacist — the following is intended only to give a background to the scientific mechanisms at play! If you think anti-depressants might help you, see your GP. If you are worried about any of the effects or side effects of a medication you are on, please see a doctor. If you are having serious thoughts of harming or killing yourself — seek medical help immediately: phone an ambulance if you can.

A Bit About the Brain

We have a wonderful introduction into how the central nervous system works over here, but the most important part for this article is that brain cells don’t actually touch each other. They communicate in the tiny gaps between each other (synapses) using substances called neurotransmitters. Once the message is sent to the next cell, the neurotransmitter substance either floats away, is attacked by an enzyme, or is reabsorbed back into the original cell like Voldemort on the back of Prof. Quirrell’s head; to stop the message from being sent more times than it should be.


For antidepressants, the neurotransmitter in question is serotonin. You may have heard of it as the “happiness hormone” in a dozen newspaper headlines, or it being involved in falling in love, or it being released when you eat chocolate. There’s a tiny bit of truth to all of these, but nothing is that simple. For the purposes of antidepressants, it is important to know that serotonin has a role in regulating mood.

For those of us with depression, serotonin doesn’t seem to work as effectively as it should. It could be that your body doesn’t produce enough of it at one end of the brain cell communications, or that it isn’t all that good at giving the wake-up call to the cell at the other end of the communication. Either way, this can lead to irregular and low moods.

Once serotonin is released by one cell, there is an enzyme that helps to break it down for reabsorbing once it’s done its job. Different classes of antidepressants affect that process in different ways, but the net result for them all is that more serotonin hangs around for a longer period of time, and there’s more chance of the message being sent as it should have been — which hopefully goes some way to make up for it being a little bit sh*t at its job in the first place.

All of these drugs take approximately six weeks to build up in your system before you start to get the best of mood improvement effects. Your doctor should be keeping a close eye on you in that time as this is when side effects are worst.

Prozac Nation: The Selective Serotonin Reuptake Inhibitor (SSRI)

SSRIs do exactly what they say on the tin: they inhibit the reuptake of serotonin back into the first brain cell. They’re selective in that some of them work in certain pathways of serotonin in the brain and focus specifically on the ones we think are responsible for low mood.

SSRIs include fluoxetine (brand name Prozac), citalopram, and sertraline. They’re the most commonly prescribed antidepressants these days.

The Power of Three: Tricyclic Antidepressants

There’s nothing particularly exciting here around three being ‘the magic number’ or anything — they’re just called that because of what the chemical compound looks like. It has three rings of atoms, hence tricyclic. They work in the same way as SSRIs in that they block the reabsorbtion of serotonin.

Tricyclics include amitryptaline, and aren’t prescribed as much anymore because they are associated with more side effects.

The Original, but Definitely Not the Best: Monoamine Oxidase Inhibitors (MAOI)

Monoamine Oxidase Inhibitors were the first lot of commercially available antidepressants, and they too pretty much do what they say on the tin. Monoamine oxidase is the enzyme that breaks down the serotonin into other products that are more easily cleared or reabsorbed. Inhibiting the enzyme means that process takes longer, and therefore serotonin is hanging about.

You’re unlikely to have heard of any of the common MAOIs, because they’re only used for depression these days when other treatments aren’t effective. Some names include isocarboxazid and nialamide, and I had to Google these because they don’t even teach us the names with our psychology degrees anymore — that’s how uncommonly used they are.

It’s  Not Quite as Simple as That!

We know serotonin has a link to regulating mood, and that the above drugs go some way to alleviating low mood, but it’s unethical to chop off the tops of people’s heads while they’re alive to make sure that what we think is going on is exactly what is going on. So far, the above is a summary of the best scientific theories of what is going on in your noggin when you take antidepressants.

It’s also not quite so simple in that serotonin doesn’t just affect your mood. Serotonin also works on your digestive system, your blood stream, and your sex drive. The obvious consequence of interfering with the way your body is managing these things is the potential for other things to change in your body with the addition of the drug. Side effects of antidepressants therefore include nausea, sleep interferences, and issues with sexual function, including loss of erection in penis-owning people, and loss of orgasm in vagina-owning people. That’s why you can only get these drugs from your doctor, and you should always have an in-depth conversation about whether or not something is right for you.

One of the most worrisome potential side effects of antidepressants is that they have an unclear link to suicidal thoughts. This is a somewhat contentious issue, and Dr Ben Goldacre of Bad Pharma fame has written much more on this than I could cover! The most important thing here though is that if you have urgent and serious thoughts of harming or killing yourself, seek immediate medical attention and call an ambulance if you are able to do so.

Of course, not everyone will experience the same side effects, and depending on how severe your depression is and how much it affects your function, it may be worth some side effects for the relief that you may get from the antidepressants. That’s why you need to have this conversation with your doctor and make the best decision for you; your body and mind.


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