What are the best drug classes for CBT?

[OzymandiAsh]

Apparently barbiturates rank at the top.

How about quaaludes?
Benzos?
Opiates? and so on.

What are the top 5 or 10 deadliest classes of drugs/substances?

 

[Chemi]

Opiates + Benzos in combination lead to respiratory depression and death. I assume that's most likely what you are looking for

 

[Liebestod]

Barbiturates are the deadliest. They are impossible to obtain.