Back in the 70s, smoking was actually recommended by mental health
professionals in some cases.  My grandmother picked up the habit in her 30s on
the advice of a psychiatrist.

Anecdotally for me, it seems to be helpful for anxiety etc.  I started
in my mid-teens.  It was a decent "social lubricant" for an awkward
little nerd.

Still, any benefit (perceived or otherwise) of smoking is outweighed by
all of the drawbacks.