How does marijuana affect the human body? How bad is it for your lungs. Is it addictive? Does the human body crave for marijuana?

See below. Aside from health and "gateway"issues, marijuana is addictive. There are cravings and a clear cut withdrawal syndrome upon cessation characterized by increased blood pressure, irritability, insomnia among others. They will last several weeks.
Marijuana . Marijuana is a mixture of green or brown shredded leaves, seeds, stems or flower of the hemp plant. It contains a chemical called tetrahydrocannabinol, better known as thc. It also contains over 400 chemicals, many of which are carcinogenic (cause cancer). All forms of marijuana are mind altering and changes how the brain works. Perceptions and thoughts can be disturbed. Marijuana use is linked to depression, anxiety, suicidal thought and an increase in psychosis. People who smoke marijanua are at higher risk for depression, poor coordination, impaired judgement, increased heart rate and heart attack and cancer. Also, people who smoke marijuana may also smoke cigarettes or do other drugs which greatly increase their risk of breathing problems and cancer. It has been found to be addictive and is considered a 'gateway' drug for other habit producing drugs as users often go on to abuse other illegal drugs such as narcotic pills, cocaine, crack, etc.