Substances give you a feeling of wellbeing that lasts for a short time. This can be enjoyable and may make you feel like you can cope more easily with problems you're experiencing. The down side of this is that you may feel you need to keep taking substances, or take more, to stay feeling that way.
Taking substances becomes a problem when you start to depend on them - when you feel you need to take a substance to feel good, or to feel less bad. This may mean that you become addicted.
Addiction can be physical and/or psychological. Having a physical addiction means that taking a substance has changed your body's chemistry so that it can't cope without that substance. A psychological addiction is said to develop when your mind, not your body, can't cope without the substance. In practice, people who use substances heavily tend to experience both physical and psychological addiction.
Misusing substances has harmful effects on your physical and mental health and it can often be difficult to separate the two. It can also affect the way you behave, causing problems in your relationships, job and daily life.
If you are worried about your own or someone else's substance misuse, you should contact your GP. He or she will be able to signpost you support.
The following links below offer more detailed information and advice on a wide range of mental health conditions:
FRANK
Alcoholics anonymous
MIND
Royal College of Psychiatrists
The Mental Health Foundation
NHS Choices