Weighing about 3 pounds and containing about 100 billion cells, when you take drugs you change the way these chemicals behave.

Most drugs work by copying or blocking your natural brain chemicals.

Drugs can actually change your brain – they can change how it works and even its structure.

These changes can be long lasting.

Drugs work in the brain by tapping into your brain's communication centre and interfering with the way your brain normally sends, receives and processes information.

Your brain is the most complex organ in your body.

It is made up of many parts that all work as a team.

Areas of the brain affected by drug use include the brain stem (controls critical functions such as your heart rate, breathing and sleep), the limbic system (responsible for your emotions) and the cerebral cortex (which processes information from your senses and contains the ‘thinking centre’ for your brain).

Psychological dependence (or psychological addiction if you like) is not just ‘wanting a drug’ or ‘not having enough willpower to stop’ – it happens when you mess around with your brain chemicals so much that your brain ends up adjusting its own chemical levels to balance itself out.

This can make it really hard to stop using drugs as your brain now needs them to make its chemical levels ‘normal’.

When you are a teenager your brain is still developing.

One of the areas of your brain that is still changing is your prefrontal cortex – this is the part of the brain that helps you assess situations, make good decisions and keep your emotions and desires under control.

Drug use during your teenage years can get in the way of your brain developing properly.

Drug use can disrupt your brain function in important areas: motivation, memory, learning, judgement, and behaviour control.

This can result in lots of problems like not doing well at school or getting into trouble with the Police.

Some drugs are toxic (poisonous) to your brain’s nerve cells and can damage or completely destroy them.

Drug use and mental health problems often go hand in hand.

Sometimes a mental health problem can lead people to take drugs.

Sometimes drug use can cause a mental health problem or make one that is already there worse.

Giving yourself a good long break from drug use (or completely packing in) will give your brain a good chance to recover and get its own chemical levels back to normal.

FDS has the kind permission of Ruth Sterry for ZigZag Young Person's Substance Misuse Service, Herefordshire to use this information.