Humans have engaged in psychoactive drug use, sometimes in formal (ceremonial) settings and sometimes recreationally, since before recorded history. It has only been in the last century or so that abuse and addiction have become large-scale problems. Using peer reviewed scholarly sources and your own insights into these issues, formulate an argument as to why the problem has reached its current scale.  In your discussion, evaluate the employment of psychoactive drugs from the aspects of a risk-benefits analysis and ethical considerations such as the risk of addiction versus the cost of punitive action. Also explain purely pharmacological issues such as pharmacokinetics and routes of drug administration and dose. If needed, include factors such as supply, cultural attitudes to drug use, and the context of drug use.