weed slightly temporarily inhibits serotonin uptake in the brain, leading to random and unconnected thoughts and impaired memory & reaction time while high. It also dilates your lungs, increases heart & breathing rates and can irritate your respiratory system. cocaine will actiually create new synapses in your brain that lack pain receptors and will only function in the presence of the drug. When you're not using you feel depressed, lethargic & unwell. It slowly breaks down your nervous, cardiovascular, respiratory & immune system, and does so slowly overtime so that lifelong addiction is very plausible.