People talk about the physical addiction to nicotine and the psychological addiction to nicotine.

人们谈论尼古丁的身体成瘾和尼古丁的心理成瘾。

Repeated use of a substance can also lead to physical addiction or substance dependence.

重复使用某种物质也会导致身体成瘾或物质依赖。

Physical addiction to heroin means it is very tough to stop taking the drug as the body changes, putting the user through traumatic mental and physical side effects.

对海洛因的身体成瘾意味着随着身体的变化很难停止服用这种药物，使使用者经历创伤性的精神和身体副作用。

Unlike cocaine, scientists say, caffeine doesn't pose a threat to society and it doesn't activate these brain reward circuits that are kinda the key to actual physical addiction.

科学家说，与可卡因不同，咖啡因不会对社会构成威胁， 也不会激活这些大脑奖励回路， 而这些大脑奖励回路是导致实际身体成瘾的关键。