If your friend smokes weed and you are concerned that it is a problem, talk to them about it. A clear sign that recreational substances, such as alcohol or marijuana, have become an addiction is when family life, daily activities, and ability to work is impeded, and/or they can't stop using the substance even though they want to quit.

Is Marijuana Addictive?

Marijuana addiction is uncommon and can only be diagnosed in severe cases. Only a small percentage of users will develop what is known as a marijuana use disorder. The number rises significantly for those who started using weed in their teens, according to the National Institute on Drug Abuse (NIDA).﻿﻿ If your friend uses pot occasionally, they likely do not have an addiction to marijuana.

Marijuana Use Disorder Rather than use the term "addiction," health professionals prefer the term "marijuana use disorder." The NIDA estimates that about 30% of marijuana users may have some degree of marijuana use disorder.﻿﻿

Marijuana Dependence

If your friend frequently uses marijuana and experiences withdrawal symptoms upon stopping the drug, they may be considered to have marijuana dependence. Marijuana withdrawal symptoms are typically mild, peak within the first week after quitting, and may last up to two weeks. Symptoms include:﻿﻿

Irritability

Trouble sleeping

Decreased appetite

Restlessness​

Marijuana Effects on the Adolescent Brain

Research has examined how marijuana affects teens. Some studies suggest that teenagers who use marijuana frequently may experience short-term effects such as problems with memory, learning, coordination, and judgment.﻿﻿

There are also long-term effects. Some studies suggest an association between regular marijuana use in teens and "altered connectivity and reduced volume of specific brain regions."﻿﻿﻿﻿ But other studies "have not found significant structural differences between the brains of users and non-users."﻿﻿

A large cohort study followed nearly 4,000 young adults over a 25-year period into mid-adulthood. It found that although cumulative lifetime exposure to marijuana is associated with lower verbal memory test scores, exposure did not affect other cognitive abilities like processing speed or executive function.﻿﻿

Studies have found that frequent use of marijuana as a teenager can be associated with an average IQ loss of eight points that were not recoverable after quitting. However, the same use in adults showed no reduction in IQ. The research data suggests marijuana's strongest long-term impact is on young users whose brains are still developing.﻿﻿

Marijuana As a Gateway Drug

Marijuana is not generally considered a "gateway drug" because the majority of weed users do not go on to use harder, addictive substances, including cocaine and heroin. Social environment might be a more critical factor in determining someone's risk for trying harder drugs.﻿﻿

If someone is more vulnerable to getting involved with addictive substances, they are more likely to start with substances that are more readily available, such as alcohol, tobacco, or marijuana. People who have social interactions with other substance users are more likely to try other drugs.﻿﻿