Overdose

Drug overdoses are caused by consuming an excess amount of drugs in a short time period, before the body has the time to deal with it.
There's also a random chance of getting an overdose from just one dose.

The severity of a Drug Overdose is determined by what drugs are consumed; with social drugs (i.e. Beer, Smokeleaf) and Luciferium not contributing to overdoses, hard drugs (i.e. Go-juice, Flake, Yayo, Wake-up) increasing the severity by 0.18-0.35 per drug consumed, and medical drugs (i.e. Penoxycyline) increasing severity by 0.08-0.14 per dose.

Stages

There are four stages of Drug Overdose in RimWorld:

• Hidden (severity: <0.50)
  • No effect, within tolerable levels of hard drug consumption
  • Doesn't show on the health tab of colonists
• Minor (severity: 0.5—<0.75)
  • Reduces the affected pawn's consciousness by 50%
  • Frequent vomiting
    • Every 0.3 days (4.8h) on average
• Major (severity: 0.75—0.99)
  • Pawn will lose consciousness (Consciousness max: 10%)
  • Chemical damage to the brain on average 2.5 days in this state
  • Death on average 3 days in this state
• Fatal/Extreme (severity: 1)
  • Overdosing pawn's body is unable to handle extreme drug levels, and succumbs
  • Still shows up as 'Major' in health tab

Drug overdose severity reduces by 1 per day, meaning that the pawn will fully recover in up to 1 day (0.5 days until no symptoms are shown).