One of the main characters becomes addicted to painkillers in the course of the series (but manges to break the habit). Drugs are very commonly used as plotpoints, such as to explain the murderers' motivations. Drug consumption is sometimes depicted. An episode deals with hallucinations due to some characters' being drugged.
Occasional alcohol consumption (beer/wine/liquor), sometimes in bars.
The main character hypnotises several people over the course of the series to quit smoking. In a quaint American way smoking is treated worse than using drugs.