If he's constantly high, that would lend itself to his behavior. I am not sure if this slime acts like narcotics do on Earth, but certain drugs that get you high can cause serious, permanent damage to your brain, and therefor your thought process. It is likely that is what has happened with him.

I also believe you should explore for other outlet options. It would be better if you had one that is actually useful, rather than one that simply fuels the fire, so to speak.