YES. Using marijuana distorts perceptions, impairs coordination, causes difficulty with thinking & problem solving, plus problems with learning/memory. In chronic users, marijuana's adverse impact on learning and memory can last for days or weeks after the acute effects of the drug wear off. So, someone who smokes marijuana every day may be functioning at a suboptimal intellectual level all the time.
Yes. Marijuana has well established a motivational syndrome as a major consequence. He marijuana addicts lose the drive to do things and the productivity diminishes over time.