The series has graphic sex scenes, but they are not very frequent.
Every episode begins with a death, the death scenes can be disturbing.
Fuck is frequent, Cunt is occasionally used, but there are many other sexually offensive terms.
All characters drink and smoke regularly, sometimes some characters use drugs like ecstasy and cocaine.
The series was banned in video rating in Singapore, is not recommended for children under 18 years in England, Brazil, North Korea (2-5 season), Australia, In Argentina and New Zealand, the series is only recommended for people over 16 years, Portugal and Germany the show is not recommended for children under 12 years.
The series is for adults, but if you watch with your 15 year old son will have no problem.
Maybe if it were a movie censorship would be:
Rated R: Strong Sexual Content, drug material, language and disturbing images throughout.
It's a great show.