Is vanillin addictive?

Always addictive.

Mushrooms are no more additive than any other foods. The hallucinogens found in some mushrooms may become psychologically additive to those will little or no will power or self discipline.

In forms yes, it is usually added to cocaine to create the feeling of numbness

Heroin is physically addictive because it is an opiate, and all opiates are physically addictive.Heroin is psychologically addictive because it produces desirable feelings and emotions in the user,...

Anything can be addictive; yes.