Since the biochemistry of psychoactive substances is usually the same for everyone we can assume that the same drug has the same effect on everyone…
BUT
- This does not mean that everyone experiences the effect the same way.
The human brain has a great capacity of learning which also includes dealing with altered states. Therefore the same dose will not feel the same way taken a hundred times later… - most of the times people sharing their drugs do not take the same amounts measured by bodyweight!
so even sharing of drugs means that the smaller friends are getting a higher dose!