What happens when people take drugs?
人们吸毒时发生什么？
There are three main classes of drugs, each of which has a different effect on the body.
主要有三大类的毒品，每一种对身体的影响不同。
Some drugs may make people feel happy, while others can make users feel tired or see things that are not really there.
一些毒品可能让人们感到愉悦，而其他一些会让吸食者感到疲劳，或者看见一些实际并不存在的东西。
Although these drugs can produce different reactions, they can all make people addicted.
尽管这些毒品会产生不同的反应，但它们都会使人上瘾。
One class of drugs is called uppers.
一类毒品被称为兴奋剂。
Uppers can increase the heart rate and make users feel very energetic and happy.
兴奋剂可以加快心脏跳动速率，让吸食者感到精力充沛，情绪昂奋。
The side effects of drugs in this class include difficulty sleeping, nervous tension, heart attacks and, in some cases, death.
这一类毒品的副作用包括难以入睡、精神紧张、心脏病，在一些个例中，还会死亡。
An example of an upper is a drug called speed, which is usually taken as a tablet or capsule.
一个兴奋剂的例子就是一种被称为“快速丸”的毒品，通常是以药片或者胶囊的形式服用。
Speed is often used as a weight-loss pill, because it reduces one's appetite.
快速丸通常是用作减肥药，因为它减少人们的食欲。
Some uppers are legal, such as nicotine, which is found in cigars and cigarettes, and caffeine, which is in coffee, tea and cocoa.
一些兴奋剂是合法的，如尼古丁，可在雪茄或香烟中找到；还有在咖啡、茶和可可豆中都有咖啡因。
As smokers may tell you, people can become easily addicted to nicotine, which is why they have trouble quitting smoking.
正如吸烟者可能告诉你的那样，尼古丁是非常容易上瘾的，这就是为什么许多人很难戒烟的原因。