Marijuana is a dry, shredded green and brown mix of flowers, stems, seeds, and leaves derived from the hemp plant cannabis sativa or cannabis indica. The main psychoactive chemical is delta-9-tetrahydrocannabinol (THC). Common terms include: reefer, pot, grass, weed, sinsemilla, hash oil, wax, etc.

• Low-grade marijuana: Where average THC levels are between 1% - 3%
• High-grade marijuana: Sinsemilla or hashish where average THC levels are between 7% - 20%
• Hash oil: Up to 70% THC

The vast majority of marijuana users smoke cannabis using hand-rolled cigarettes (joints), pipes, bongs, or marijuana cigars (blunts). When marijuana is sold or consumed for medicinal purposes, it is often mixed into a variety of foods (edibles) including chocolate, brownies, cookies, or candies.

The use of marijuana extracts or THC-rich resin is on the rise. Users refer to this practice as dabbing. Various forms of these extracts include:

• Hash oil or "honey oil"- a gooey liquid
• Wax or "budder"- a soft solid with a texture like lip balm
• "Shatter"- a hard, amber-colored solid.

These extracts deliver extremely high amounts of THC to users. Their use has sent a number of users to the emergency room (panic attacks, psychosis). Sometimes users forgo inhaling smoke and use vaporizers.

• Daily cannabis use is now at the highest rate among college students in more than three decades.
• Marijuana has remained the most widely used illicit drug over the 34 years that MTF (Monitoring the Future) has tracked substance use by college students, but the level of use has varied considerably over time. In 2006, 30% of the nation's college students said they used marijuana in the prior 12 months, whereas in 2013 nearly 36% indicated doing so.
• Of perhaps greater importance, daily or near-daily use of marijuana—defined as 20 or more occasions of use in the prior 30 days—has been on the rise. The recent low was 3.5% in 2007, but the rate had risen to 5.1% by 2013.

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Marijuana affects several parts of the brain, including those responsible for memory, learning, coordination and sensory and time perception.

• Hypothalamus: Increased appetite
• Ventral striatum: Euphoria and relaxation
• Amygdala: Increased anxiety and paranoia
• Neocortex: Altered senses and disordered thinking
• Hippocampus: Impaired learning
• Cerebellum: Decreased motor control

• Altered senses- i.e. seeing brighter colors
• Altered sense of time- i.e. time seems to slow down
• Changes in mood- typically a euphoric response, but could also include paranoia, anxiety, or other responses
• Impaired body movement
• Difficulties with thinking and problem-solving
• Impaired memory (short-term)

• Lung Health: Guess what...? Anything that is burned and smoked is probably not great for your lungs. Studies of chronic, heavy marijuana smokers show that their lungs do not produce as much airflow as the lungs of non-smokers do.
• The Heart: Marijuana use increases heart rate and may decrease the heart's pumping efficiency during exercise. Those with heart disease or high blood pressure should be aware of this.
• The Reproductive System: Marijuana suppresses the production of hormones that help regulate the reproductive system. This translates to decreased sperm count and occasional erectile dysfunction in men and irregular menstrual cycles in women. The probability of conception is also decreased.

Anxiolytic or Anxiogenic? There has been a long time debate about whether cannabis reduces or increases subjective levels of anxiety in users. Research suggests that while marijuana may help some users "relax," in some users it can induce anxiety or panic attacks. It may also increase habitual users' baseline level of anxiety over time (the "yo-yo" or "going up the stairs" effect). It is also important to note that one-time use with a high-concentration THC product for a relatively inexperienced user can result in an anxiety or panic attack.

Cannabis and Psychosis: Cannabis has been linked to the onset of psychotic symptoms in users (hallucinations, delusions, paranoia). Users that are most prone to this reaction are those with a family history of psychotic disorders such as schizophrenia.

Myth #1: Marijuana increases quality of sleep.

Fact: THC may help you fall asleep, but the quality of your overall sleep may be worse when using marijuana. Persistent use is likely to increase insomnia and poor-quality sleep when cannabis use is discontinued. Marijuana use decreases the length of REM (Rapid Eye Movement) sleep, the most restorative stage of the sleep cycle^.4

Myth #2: Marijuana is a cure for anxiety.

Fact: The most commonly reported side effects of smoking marijuana are intense anxiety and panic attacks. Studies report that about 20% to 30% of recreational users experience such problems after smoking marijuana. The people most vulnerable are those who have never used marijuana before.⁵

Myth #3: Marijuana is not addictive.

Fact: There are currently 2.7 million Americans meeting the criteria for cannabis addiction. Estimates suggest that 9% of adults and 17% of adolescents who choose to use marijuana will develop a dependence upon it for daily functioning.⁶

Myth #4: Smoking marijuana is a safe alternative to smoking tobacco.

Fact: Marijuana smoke contains 50-70% more carcinogenic hydrocarbons than tobacco smoke. Marijuana users usually inhale more deeply and hold their breath longer than tobacco smokers do, which further increases the lungs' exposure to carcinogenic smoke.⁷

Using marijuana during college can negatively impact your academic experience and educational outcomes. Listed below are some common ways marijuana use, and more specifically, habitual marijuana use, can negatively impact your academic achievement at Caltech.

• Motivation: Some marijuana users experience what is called "amotivational syndrome." This is a significant reduction in personal ambition and a desire to achieve goals. It takes a healthy amount of stress and motivation to be successful in college. For some users, complacency can lead to decreased academic performance.
• Learning: Marijuana use has been shown to disrupt short-term memory formation in the hippocampus. This is important for students because short-term memory formation is vital to the learning process. Habitual cannabis use can lead to difficulties retaining and learning the material covered in lectures or read in textbooks.
• Attention & Concentration: Smoking marijuana can also disrupt the frontal lobe and executive functioning. The most notable of the executive functions are attention and concentration. Heavy users may have increased difficulty sustaining attention, shifting attention to meet the demands of changes in the environment, and registering, processing, and using information.