What effects do peaple want to achieve when they abuse these

What effects do peaple want to achieve when they abuse these drugs?
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Using drugs carries a range of physical and mental health risks, and the only way to eliminate these is not to use any drugs at all. However, this may not be realistic when the decision to use or not to use a particular drug is a matter of personal choice, but it must be acknowledged that when choosing to use a drug, a person must accept the associated health risks.
All drugs will affect the user's judgment and probably reduce their inhibitions, increasing the likelihood that they may find themselves in situations they would normally avoid and which may be unsafe. Sexual situations may be more likely to occur when drugs are involved and it may be harder to remember the importance of practicing safer sex when using drugs, thus increasing the risks of unplanned pregnancy and sexually transmitted infections (including HIV).
Different drugs carry different risks. You will find more information about the specific risks associated with each of the drugs listed in our section on 'Drug Types', but there are also general factors to consider:-
Drug effects and risks are the result of the interaction between three factors:
DRUG FACTORS - everything connected with the substance itself and how it is taken.
Different drugs carry different risks. For example:
Some drugs act as 'Stimulants', increasing the activity of the central nervous system, so anyone with a heart condition, respiratory problems and/or epilepsy should definitely not take them.
Some drugs can lead to 'Physical or psychological dependence' if they are taken regularly.
Some drugs are a particular danger to people who have or are unaware they have a mental illness, as the drug can bring this on. Similarly certain drugs may trigger a psychotic response in some people.
'Hallucinogenic' drugs can lead to people becoming very disturbed and doing dangerous things, especially if they are already anxious or depressed.
The risks of drug use also vary with:
How strong the dose of drug taken.
How often it is taken.
What else might be mixed in with it. Many illegal powders and tablets are adulterated and have all sorts of contaminants mixed with them, such as chalk, talcum powder, brick dust etc.
Whether different drugs are taken together. It is more dangerous to be under the influence of more than one drug at any one time.
How a drug is taken. Injecting tends to be the most dangerous drug taking method.
THE USER - factors concerning the user, especially their physical and mental health.
Drug risks also depend on:
Physical health. Heart and blood pressure problems, asthma, diabetes, epilepsy and liver problems can make drug use more dangerous.
Mental health. People who are anxious or depressed often find drug use makes them feel worse and can lead to them endangering themselves or others.
Body weight. Lighter people find the same amount of a drug affects them more than for a heavier person. People with eating disorders can also find drug use makes it worse.
Lack of knowledge and experience. Somebody new to drug use may be unsure what to expect or do, anxious and more likely to have problems. A small amount of a drug may be more likely to have a big effect.
Gender. Drug use can effect males and females differently because of different body weight, physical make up and the different expectations of males and females.
THE SETTING - what the user is doing at the time, where they are and who they are with.
Where people are and what they are doing whilst on drugs can also have a bearing on the risks involved. Examples include:
Taking drugs in dangerous, out of the way environments. Using drugs near riverbanks, main roads, railway lines or in derelict buildings, increases the likelihood of accidents and means help is not at hand if needed.
Driving a car or bike or operating machinery whilst under the influence of alcohol or other drugs. Again accidents are more likely.
Use of 'Ecstasy' in crowded, hot clubs and dancing non stop for hours, without drinking fluids or taking a rest, has led to people overheating and dying from dehydration and heat exhaustion.
Being under the influence of of drugs may increase the likelihood of having unplanned sex and make it more difficult to practice 'Safer Sex'.
参考资料：http://www.shef.ac.uk/drugs/health/d_hmain.htm