Working with ayahuasca for several years in a traditional (Shipibo) context has showed me just how bad cannabis can be- it is more difficult to clean out of the body (energetically/spiritually) than any other drug. It creates so many associations in our mind- memories, relationships, pains, emotions, etc.. When "on the path" (meaning, apprenticing and learning how to work with ayahuasca), it really needs to be cleaned out for useful visions to open up (to work on other people) and to be able to cleanly connect to and call in the medicinal spirits/doctors (through the icaros/songs). It can really blunt dreams, intuition and senses.

(Yah this probably sounded woo-woo, but I am speaking from a different, non-western context/lens that views this as a spiritual malady. So take that as you will)