I believe drugs and alcohol lower some type of natural spiritual protection that humans are born with, which allows the influence of demonic entities to various degrees. The bath salts seem to completely eliminate this protection temporarily so that what seems like a full blown possession takes place.

I have personal experience which may indicate the demonic influence hypothesis. In the past my wife told me on more than one occasion that I would sometimes act like a demon when I would drink excessively, saying and doing completely out of character things of a negative nature. Also, during a few phases of heavy marijuana use in my past, it would eventually lead to a change in my thought patterns so that I was overcome with negative thinking that seemed to be totally random at times and come out of nowhere. These thoughts would completely subside when the effects of the drug wore off. Another interesting correlation is that I seemed to have an abundance of demonic visitations (they would appear like grey aliens but with orange skin) in the early morning after a heavy night of drinking. Perhaps they knew that they could get to me easier in this weakened state.

  My bio dad is an alcoholic. When he's in a sober cycle, he's a great person, sensitive, spiritual, kind, a talented musician, etc.

  A number of years ago, he lost his job due to his addictions, and asked me if he could move in with me to get his feet on the ground. 

  I said yes.  It soon became clear that he was in a self destructive, addict phase, and I could practically see the dark nonphysicals hanging around him, like a dark cloud just waiting to try to influence him. At one point, he started a physical confrontation with me, after I called him out on some stuff. 

   Yes, it's very true that alcohol and drug use can open people up to being more influenced than they would be normally.  Full possession is somewhat rare, but for those alcoholics whom experience "black outs", this is what happens when full possession that happens. 

  Most often, it's more subtle influencing. Injecting negative feelings, thoughts, perceptions, and feelings into a person's energy field. 

  This also happens to people not taking substances, but it's harder to induce such people to more extreme actions, beliefs, thoughts, feelings, than when they are drunk or high (unless the person in question is really lacking in Love and very negative, then they can be very influenced).

  Perhaps somewhat contradictory, I don't think that weed or most other drugs should be completely outlawed/illegal. This seems to make the situation worse for the society in question.  Rather, focusing on holistic education, counseling, etc, seems to work better, as Portugal and other countries have shown.

  And look what happened in the US when alcohol was banned.  You can't legislate positivity, desire for true health, and/or wisdom into the hearts of others.

When I was about 30, I set up my girlfriend Marilyn and I on a blind double date with my friends Russ and Mary.  We ate out and went dancing and everything was fine--until the end of the date at Marilyn's apartment.  Without consulting me, Russ distributed joints.  Marilyn and Mary gasped, carefully scrutinizing my disapproval at being blindsided like this.  Russ and Mary were very nervous around each other in any case and I sensed that their potential relationship would be quickly aborted by an embarrassing scene. 

So I pulled a Bill Clinton.  I smoked a joint, but didn't inhale.  The result?  Russ and Mary now have 3 grown children! So when people ridicule Clinton's claim that he dmoked marijuana but didn't inhale, I can believe it.  I didn't either, not because I didn't want to get high, (Everyone got high except me!), but sadly because I had no idea how to smoke a joint!  Sigh!  I rationalized my flight into decadence that it facilitated a good marriage.