With long-term use, changes in the brain can occur that lead to problematic use, or cannabis use disorder. This disorder, in which a person experiences withdrawal symptoms when not taking the drug, may affect about 30% of people who use cannabis, according to the National Institute on Drug Abuse (NIDA). 

Of these individuals, about 9% may develop an addiction. A person has an addiction when they cannot stop using a substance. 

The Sf 420 delivery add that up to 17% of those who start using cannabis in their teens may become dependent on it.

Weed, general term for any plant growing where it is not wanted. Ever since humans first attempted the cultivation of plants, they have had to fight the invasion by weeds into areas chosen for crops. Some unwanted plants later were found to have virtues not originally suspected and so were removed from the category of weeds and taken under cultivation. Other cultivated plants, when transplanted to new climates, escaped cultivation and became weeds or invasive species. The category of weeds thus is ever changing, and the term is a relative one.