"Trainspotting" is one of the few movies that make you understand how a "bad person" feels, without being glorifying.
Mark Renton is a drug addict, and everything is told from his point of view. At some parts he says what a great feeling the consume is, on the other hand we see many disantvantages, too. Even though he seems to be in control from the first moment, in the end, Mark is a lonesome guy who fights his endless fight agains addiction. He does not realise how things get out of control, how his friends - except Spud - only use him and how addicted he really is. Ewan McGregor does a great job as Mark Renton, the Oscar-nominated script is excellent, the cinematography and some scenes overall are just superb and the soundtrack - a mix of rock and eurodance - is great.
There is a detailed scene where we see three couples (?) having sex at the same time (i'm not a person who says sex is a big deal, but i want you to know before showing this to your child).
There is an INCREDIBLY big amount of drugs in the movie and it is extremely detailed. We see needles with Heroin being injected, drug dealing, hallucinations, one "horror trip" (it is not too frightening, but we see Mark is very scared and in panic). Really, the drugs are lengthy, and you see all of the things relate such as hallucinations, incontinence (gross!) and the addiction.
However, it is depicted neutral. We see some disadvantages, but also it is mentioned to be a great feeling.
But it is not glorifying, either.
Know your child about the drugs.
There is very strong and very frequent language.
The movie is nowhere meant for younger viewers, strictly for older teens and adults.