Yes it is easy and that reminds me of my friend, he used to tell us he can see spirits and talk with them when he is drunk...well none of us believed him, we were 17!
And one day he just drank a lot and said he will go home all by himself and next day we hear he jumped from his building!
As to why it is? -
Any time you are sad, depressed,feeling low or just want to escape your realities for a while, you invite spirits to talk to you.
You just reach that 'vibrational state' that spirits can communicate and contact easily. Especially the sad ones, they start coming to you because they 'feel' you are in same state as they are.
Everytime you do something that does NOT involve a lot of brain work, you are closer to nature and yourself and spirits and everything.
And as much as I know about drinking or getting high... it is mainly to chill and to stop thinking about problems for a while.