Marijuana is psychoactive.  Anandamide is involved in regulating mood, memory, appetite, pain, cognition, and emotions. When cannabis is introduced into the body, Delta-9-tetrahydrocannabinol (THC), interferes with all of these functions.   

THC starts this process by binding to the CB1 receptors for anandamide. These receptors then modify the activity of several intracellular enzymes, including cAMP, whose activity they reduce. Less cAMP means less protein kinase A. The reduced activity of this enzyme affects the potassium and calcium channels so as to reduce the amount of neurotransmitters released. The general excitability of the brain’s neural networks is thus reduced as well. It also affects dopamine.    

All of these things affect ones mental process or behavior.  They affect the very core of your brain.
That is why you get pain relief, that is why you get high.  It has medicinal uses, YES,  but please don't drive. You cheapen your argument
By not knowing the science.