What is cannabis?

Cannabis (also known as marijuana) is the dried flowers, leaves and stems of the Cannabis sativa plant. The main active ingredient in cannabis is THC (delta 9 tetrhydrocannabinol). Cannabis can range from 1% THC to 8%. Hashish can be 7% to 14% THC and hash oil is up to 50% THC. THC is a fat soluble substance and can remain in the lungs and brain tissue for up to 3 weeks. There are over 200 nicknames for cannabis, including pot, herb, mary jane and chronic.

How is cannabis used?

Cannabis is usually smoked, using a pipe, a bong or by rolling a joint. Blunts are cigars that are emptied of tobacco and refilled with cannabis, sometimes in combination with other drugs. It can also be eaten in food, for example, by baking it in brownies.

Why do people use cannabis?

Smoking cannabis can relax a person and elevate their mood. This can be followed by drowsiness and sedation. Other effects include heightened sensory awareness, euphoria, altered perceptions and feeling hungry ("the munchies"). High concentrations of THC may produce a more hallucinogenic response.

Are there short-term dangers of smoking cannabis?

Discomforts associated with smoking cannabis include dry mouth, dry eyes, increased heart rate and visible signs of intoxication such as bloodshot eyes and puffy eyelids.

Other problems include:

  • Impaired memory and ability to learn
  • Difficulty thinking and problem solving
  • Anxiety attacks or feelings of paranoia
  • Impaired muscle coordination and judgment
  • Increased susceptibility to infections
  • Dangerous impairment of driving skills. Studies show that it impairs braking time, attention to traffic signals and other driving behaviors.
  • Cardiac problems for people with heart disease or high blood pressure, because cannabis increases the heart rate
  • It is virtually impossible to overdose from cannabis, which sets it apart from most drugs.

Are there long-term consequences to smoking cannabis?

Respiratory problems

Someone who smokes cannabis regularly can have many of the same respiratory problems as cigarette smokers. Persistent coughing, symptoms of bronchitis and more frequent chest colds are possible symptoms. There are over 400 chemicals that have been found in cannabis smoke. Benzyprene, a known human carcinogen, is present in cannabis smoke. Regardless of the THC content, the amount of tar inhaled by cannabis smokers and the level of carbon monoxide are 3 to 5 times higher than in cigarette smoke. This is most likely due to inhaling cannabis more deeply, holding the smoke in the lungs and because cannabis smoke is unfiltered.

Memory and learning

Recent research shows that regular cannabis use compromises the ability to learn and to remember information by impairing the ability to focus, sustain, and shift attention. One study also found that long-term use reduces the ability to organize and integrate complex information.

In addition, cannabis impairs short-term memory and decreases motivation to accomplish tasks, even after the high is over. In one study, even small doses impaired the ability to recall words from a list seen 20 minutes earlier.


Long-term cannabis use suppresses the production of hormones that help regulate the reproductive system. For men, this can cause decreased sperm counts and very heavy users can experience erectile dysfunction. Women may experience irregular periods from heavy cannabis use. These problems would most likely result in a decreased ability to conceive but not lead to complete infertility.

Is cannabis addictive?

No one would argue that cannabis is as addictive as alcohol or cocaine. However, it's wrong to say that it is not at all addictive. More and more studies are finding that cannabis has addictive properties. Both animal and human studies show physical and psychological withdrawal symptoms from cannabis, including irritability, restlessness, insomnia, nausea and intense dreams. Tolerance to cannabis also builds up rapidly. Heavy users need 8 times higher doses to get the same effects as infrequent users.

For a small percentage of people who use it, cannabis can be highly addictive. It is estimated that 10% to 14% of users will become heavily dependent. More than 120,000 people in the US seek treatment for cannabis addiction every year. Because the consequences of cannabis use can be subtle and insidious, it is more difficult to recognize signs of addiction. Cultural and societal beliefs that cannabis cannot be addictive make it less likely for people to seek help or to get support for quitting.

How do I recognize a problem with cannabis?

Some warning signs are:

  • More frequent use
  • Needing more and more to get the same effect
  • Spending time thinking about using cannabis
  • Spending more money than you have on it
  • Missing class or failing to finish assignments because of cannabis
  • Making new friends who do it and neglecting old friends who don't
  • Finding it's hard to be happy without it

Because THC is fat soluble and remains in the body for up to 3 weeks, it's important to remember that withdrawal symptoms might not be felt immediately. If you find that you can't stop using cannabis, then remember, there's help on campus.

Is cannabis prohibited on campus?

The University of California prohibits the use, possession and sale of cannabis in any form on all university property, including university-owned and leased buildings, housing and parking lots. Cannabis is also not permitted at university events or while conducting university business. For more information, see UC guidance on use and possession of cannabis on UC property.

What about the medical use of cannabis?

Cannabis' ability to enhance appetite has led to its medical use to reduce the physical wasting caused by AIDS and to reduce nausea for chemotherapy patients. According to the cannabis Policy Project, 11 states have laws that allow patients to use medical cannabis despite the prohibition by federal law. For more information on state and federal laws, go the cannabis Policy Project.

How do I help a friend who's having trouble with drugs?

If you are concerned about a friend's drug or alcohol use, this page contains information about different ways to help them.

Resources at UCSC and in Santa Cruz

Resources at UCSC and in Santa Cruz

If you or a friend are having trouble with drugs or alcohol, or just have questions, there is help available. Please contact SHOP:

The Good Drugs Guide:
This British harm-reduction web site provides extensive information on marijuana, including the basics, dangers, debates over legalization, and links.

PBS Frontline Program:
This PBS Front-line program goes behind the scenes of America's marijuana industry, examining the production, sale and effort to eradicate the use of this drug. Topics include the criminal justice system, marijuana's treatment in popular culture and efforts to prevent use by teenagers. Online features include interviews, video excerpts and health effects of marijuana.

Marijuana Anonymous:
MA uses the basic 12-step recovery program for people who are addicted to marijuana. Online groups are available, as well as publications, frequently asked questions and 12 questions to determine if marijuana is a problem in your life. The literature section has stories by teens, help for loved ones of marijuana addicts, and the dangers of cross addiction. For information about local Santa Cruz MA Meetings, please call (831) 427-4088.


Cannabis eCHECKUP TO GO is a free, anonymous assessment tool that provides individualized feedback on the role cannabis is playing in your life. You can also see how your use compares with other college students. If you would like to talk to someone about your use, you can call SHOP at (831) 459-1417 for an appointment.

Medline Plus

This search page will give you links to marijuana facts, prevention and screening, research, treatment and statistics. Fact sheets available in Spanish.

National Institute on Drug Abuse (NIDA)

This site has statistics, drug information and recent research reports on cannabis.

Take a Cannabis Tolerance Break

If you use cannabis, at some point you should take a tolerance break. Like anything else, your body builds up a tolerance: you need more to get high. A t-break could help you save money and also keep balance. Link used with permission of UVM.