In order to try to understand a little about how drugs work, it is best to first learn a few facts about the brain. Each human being has:

One head
One brain
Each brain has somewhere around 10,000,000,000 brain cells.
Each brain cell has lots of connections with other brain cells by means of nerve fibres (the wiring connecting brain cells together). There are about 4 million miles of nerve fibres in each brain. Some fibres may have up to 10,000 branches in them.
Each brain cell has lots of connections with other cells, possibly over 25,000! The junctions at the end of the neurones are called synapses.

As you can see, overall the brain is an extraordinarily complex part of the body.

For a better quality set of drawings and pictures, click here, although they will take a little longer to load.

Synapses are very important because;-

1. They are the route by which brain cells talk to each other
2. Synapses are of the same basic design in the brain, the heart, the legs etc.
3. There are a lot of them
4. If we can get chemicals (e.g. drugs) into the gap between them in the brain, we can affect the way in which brain cells talk to each other e.g. we can slow the messages down, speed the up etc.

In the drawing you will see the following;-

• Axon - A neurone (or cell body) has many axons (or nerve fibres).
• Vesicles - these contain the transmitter.
• Transmitters - these are small chemicals used by brain cells as messengers. They are stored in the vesicles in the nerve ending ready to be released
• Receptors - these are structures on the surface of the receiving cell which have a space designed just for the transmitter (if the transmitter is a key, receptors are the lock into which they fit)
• Enzymes - these surround the synapse and break down any spare transmitter that might leak out to other synapses nearby.
• Electrical signal - This is the way in which one brain cell sends a message to another. The signal travels down the nerve fibre rather like an electrical "Mexican Wave".

3. WHAT HAPPENS WHEN A MESSAGE IS PASSED FROM ONE CELL TO ANOTHER

Depending on your browser, the pictures and words may not match perfectly, but they are both in numerical order so you should be able to work it out.

Important points;-

• The passage of messages only works one way or one direction
• There is only one type of transmitter per synapse
• The transmitter allows an electrical message to be turned into a chemical message and back into an electrical message.

Although there are over 80 known different "transmitters" in the brain, each nerve ending only has one type. These "neurotransmitters" tend to be grouped together and each seems to have specific roles e.g.;-

In many mental health problems, it is known that some of these transmitters get out of balance e.g. you have too much or too little of a particular transmitter.

People with depression usually have problems with poor sleep, low mood and appetite, loss of energy and interest or pleasure etc. It is a common illness, affecting 3% of the population per year. The main theory about why this happens is the so-called "monoamine hypothesis".

We know that serotonin and noradrenaline in the brain are involved with control of sleep/wake, emotions, mood, arousal, emotion, drive, temperature regulation, feeding etc. Thus, if a person has too little serotonin and noradrenaline in the part of the brain that controls mood, this will produce too little activity, and that part of the brain become slower and less effective. This will lower mood.

In depression, it is known that there are reduced levels of serotonin and noradrenaline. These reduced levels lead to a lowering of mood. The full reasons are not fully known but stress may well play a part in causing this.

There are lots of other theories about how depression occurs e.g. genetics, how the brain develops, stress etc. There may in fact be many causes and in each person there may be a combination of these. Stress may in fact cause changes in the brain which then result in reduced levels of serotonin and noradrenaline. Transmitters other than much serotonin and noradrenaline are probably also involved.

If too little serotonin (or noradrenaline) produces the symptoms of depression then correcting this should help to reduce the symptoms. One way of doing this is to block the reuptake (recycling) of transmitters. This is just what an SSRI antidepressant does. They block the reuptake of serotonin, so the next time an impulse comes along, there is more transmitter, a stronger message is passed, and activity in that part of the brain is increased.

The important thing to remember is that SSRI antidepressants probably mainly work by correcting the effect of having too little transmitter. They are NOT JUST STIMULANTS. They have a much more specific way of working than just stimulating you.

SSRI antidepressants mainly block the reuptake of just serotonin. This why they are called the SSRIs ie. Selective Serotonin Reuptake Inhibitors.

Many other antidepressant drugs also affect other transmitter systems e.g. acetylcholine, dopamine, histamine etc. and have many side effects. SSRIs really only block the reuptake of serotonin, and so have less side effects. However, they still have some side effects ;-

• Too much serotonin in some parts of the brain can make you feel sick, less hungry and get headaches or migraines
  

8. DO THE SSRIs WORK, AND FOR HOW LONG?

The big questions for people with depression are do the drugs really work and, if so, how long do you need to keep taking them for?

In people who have had more than two episodes of "major" depression, and got better with antidepressants, research has now shown that over the next three years;-

• Less than 1 in 4 people who carry on taking an antidepressant become depressed again
• Nearly 9 out of 10 people who do not take an antidepressant become depressed again

If you stop your antidepressant after you have got better, you are six times as likely to become depressed again within three years

• 2 out of every 3 people who stop their antidepressant after three years become depressed again within the next two years
• Only 1 in 20 people who carry on with an antidepressant become depressed again

We do not know for certain what happens after five years. Many people may be advised to carry on with an antidepressant for longer but that is a decision for you and your doctor to make.

Antidepressants can be very effective in treating depression. For many people, however, depression can come back. Antidepressants are also very good at stopping depression coming back, but only if you keep taking them.

Some key facts about antidepressants;-

• The symptoms of depression are caused by an imbalance of chemicals in the brain, probably reduced levels of serotonin and noradrenaline
  
• Antidepressants help correct this imbalance in the brain
  
• Antidepressants are not stimulants
  
• They do not alter personality
  
• They are not addictive and are not habit forming (but you should not stop taking them suddenly)
  
• They do not lose their effect if you keep taking them

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Many developments have been as a result of feedback from visitors.

No site can be entirely bias-free. No matter how hard someone tries, training and background will always influence your outlook. We have, however, tried to eliminate bias, and we hope you take these pages in the spirit in which they are provided i.e. a genuine attempt to inform, educate and support.

Information here is based on published data. References include the UK British National Formulary (BNF, published by the British Medical Association and Royal Pharmaceutical Society of Great Britain), Martindale (the extra pharmacopoea, published by RPSGB Pharmaceutical Press), Psychotropic Drug Directory (latest edition), Data Sheet Compendium (UK Manufacturers Data Sheets, published by the Association of British Pharmaceutical Industry), MicroMedex (an independent and extensive CD-ROM based drug information source), UK Psychiatric Pharmacy Group leaflets, Royal College of Psychiatrists advice and guidelines and the current medical literature. Thanks also to all those people who left e-mail comments, suggestions and requests, who have helped shape the site.