Only indirectly. More precisely the difficulty is based on supply of hashing power. If more people hash, the blocks will be minted faster and the difficulty will be adjusted higher at the next re-adjustment. It doesn't really matter if those blocks are actually full or empty, and in fact the system would continue to work if most of the blocks were empty and the trading happened off the chain in exchanges.
I say indirectly because the amount of hashing power on the chain at any given moment is driven by the expected reward per block minted. Nobody wants to run thirsty machines if the cost of electricity exceeds the expected rewards for successfully minting a block. So the number of machines online and is directly proportional to the value of bitcoin, which is driven by consumer demand.