The Oxford dictionary disagrees with you. Check it.
From the Oxford Dictionary of the English Language:
|ˌinəzˈmə ch |
adverb ( inasmuch as)
to the extent that; insofar as : these provisions apply only inasmuch as trade between Member States is affected.
• considering that; since (used to specify the respect in which a statement is true) : a most unusual astronomer inasmuch as he was deaf-mute.
ORIGIN Middle English : originally as in as much, translating Old French en tant (que) ‘in so much (as).’
You need a full verbal clause, and not a given phrase like that one. Say, if "concerned" in that sentence meant "worried", then it would be grammatically correct.