SSRIs – understanding how they work

Selective serotonin reuptake inhibitors (SSRIs) are commonly prescribed to treat depression and other psychiatric disorders such as anxiety, OCD, PTSD etc. 

SSRIs have gained in popularity since they were first introduced in the late 1980s due to the fact that they exhibit less severe side effects from the classes of anti-depressants that preceded them. They are not without side effects or controversy though, which will be mentioned later, but most GPs will often prescribe SSRIs for moderate to severe depression.  Where depression is considered to be mild, talking therapies are sometimes the first intervention recommended, notably CBT.  SSRI prescription can be subject to trial and error until a suitable product is found that is tolerable for the patient.  It can take 4-6 weeks before the effects of the medication are noticed.

How they work?

Although SSRIs have been in use for over 30 years, it is not exactly clear how they work.  It is believed that consuming SSRI medication increases certain neurochemicals (neurotransmitters) in the nervous system.  Some of these neurotransmitters have a direct effect on our mood and emotions.  In particular the neurotransmitter serotonin which plays a key role in our mental well being.

It is believed that SSRIs inhibit the reuptake of serotonin and thereby increase the availability of this neurotransmitter in the brain and other areas of the nervous system.

To understand how they work it is necessary to have a basic grasp of how our brain is wired and the electro chemical connectivity that is constantly occurring.

Neurons and their activities

Our brains consist of around 100 billion nerve cells which are wired together in a complicated tangled structure. Each nerve cell, called a neuron, can receive and transmit an electrical signal and has many connections (thousands) to and from other neurons.  Any signal travel through a neuron is essentially a piece of information, a message.

When signals are received by a neuron from the many other neurons it’s connected to, eventually a threshold level is reached whereupon an electrical charge is generated and travels along the cell’s axon.  At the end of the axon, the axon terminal is reached which is essentially the end of the neuron.  Here the electrical impulse is converted into a chemical i.e., a neurotransmitter.  The axon terminal releases this neurotransmitter which then travels across a gap or synapse to the neighbouring neuron where it is received at the dendrite, converted into an electrical signal and the process repeated.  Excess neurotransmitters or those that weren’t used are then absorbed by the neuron.

SSRIs are thought to work by blocking this reabsorption process thereby increasing the availability of serotonin and other neurotransmitters at the synapse.


Approximately one third of people prescribed SSRIs will enjoy a noticeable or beneficial effect on their depression.  For the remaining two thirds, there will either be no effect or only partial relief from the symptoms of depression.

A 6 year meta-analysis found that SSRIs were more effective than placebos in adults with depression however opinion on their effectiveness remains divided and the exact effect that increased serotonin levels have in general is not widely agreed upon. 

Side effects

Depression is an extraordinarily complex condition and it remains the case that there is no single universal cure for it, although SSRIs can help some people.  Many doctors do agree that sometimes the side effects of SSRIs can be severe and range from nausea, vomiting, weight gain, gastrointestinal problems, headaches to serotonin syndrome (a potentially life threaten condition resulting directly from too much serotonin). 

Perhaps it’s not surprising that some of the stomach related side effects occur due to the fact that around 80% of serotonin is produced in the gut where it is used as both a neurotransmitter and hormone.

Since it’s not possible to selectively increase serotonin levels i.e only increase those in the brain and nowhere else, it follows that an increase in levels overall will simultaneously affect both the brain and stomach.

It’s difficult to determine in advance if you will suffer from side effects or whether the particular SSRI you take will have a beneficial effect.  For this reason, finding an SSRI that will work can sometimes be a frustrating process involving trying out a number of different products over a period of time.

Alternatives to medication

If you are currently prescribed and taking SSRI’s or other medication for depression or psychiatric disorders, then it is important that you continue to take your medication as directed and any changes that you wish to make or side effects that are observed, should be discussed with your GP.  If you wish to stop taking medication then this needs to be under the supervision of your GP.

Psychotherapy has a good track record of helping with depression. Solution Focused Hypnotherapy combines psychotherapy with hypnosis and this also has a proven track record of being beneficial to depression sufferers. 

In many cases therapy provides the catalyst for change and change can help move forward from a stuck position.  One of the benefits of the solution focused approach is that is does not overly dwell on the problem but rather it focuses on the journey towards the life you want instead.

Whether you are on medication or not, it is worth considering psychotherapy as an extra attack vector in the battle against depression so that a rewarding and happy life can be lived.

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