Chapter 5

What You Need to Know About Cannabis

Cannabis (marijuana) is a drug that many people use, some regularly with no apparent negative effects. However the other side of the story is that this drug can be a trigger to mental disorders, particularly for those who may be pre-disposed to have a mental illness. And cannabis can contribute to other negative effects and potential harm. Remember too that there are different strengths of cannabis. Over the years the strength of the commonly available cannabis, often called skunk, is much stronger and potentially more harmful than the cannabis used many years ago. So remember, cannabis is not a harmless drug. This chapter helps you learn how the use of cannabis can affect your child’s memory, learning, and performance of physical activities. At the end of this chapter we also present information about other drugs and their negative effects.

Cartoon of a Cannabis Leaf

Street Names For Cannabis

There are more than 200 slang terms for cannabis, varying from city to city, and neighborhood to neighborhood. Some common names are marijuana, hashish, pot, grass, herb, weed, Mary Jane, reefer, skunk, boom, gangster, kif, chronic, and ganja.

Cannabis Is a Powerful Drug

One effect of cannabis is that it can cause some people to lose focus on events around them. For some this may seem to be an enjoyable experience. This happens because cannabis causes some parts of the brain -- the parts associated with motor coordination, emotions, memory and judgment -- to go out of balance and control. When this happens, a drug user may make unhealthy behavior choices.

Some examples of the negative effect cannabis can have:

And bear in mind: High doses of cannabis use may lead to anxiety and panic attacks.

All these different changes are caused by chemicals that affect the brain. Cannabis contains a chemical called delta-9-tetrahydrocannabinol, better known as THC. Quite a lot of other chemicals are found in marijuana, about 400 of them, some of which can cause lung cancer. But THC is the main active ingredient.

Cannabis Invades the Brain

Within minutes of inhaling, a user begins to feel "high," or filled with pleasant sensations. The THC chemical in cannabis causes this big impact on the brain.

Cannabis Invades the Brain

For some this is and remains a pleasant and temporary sensation. But depending on the person, the situation, the strength of the cannabis it can become harmful and even dangerous both to the user and to the relationships with his or her friends and family.

What happens when cannabis hits the brain?

Cannabis affects coordination, learning and emotions

Motor Coordination

Imagine you are watching your teen playing soccer. An easy pass comes his way, and he has the chance to score the winning goal. But today, he seems a bit off his game. He fumbles; an opponent seizes the opportunity and kicks the winning goal. Game over. Such loss of coordination can be caused by smoking or ingesting cannabis.

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Why does this happen?

THC can find its way into the cerebellum, the section of our brain that does most of the work on balance and coordination. With THC in the brain, scoring a goal in soccer may become a bit tough, but it can spell disaster on the highway when a driver’s response times are slowed by the drug. Research shows that drivers (of any age) on cannabis have slow reaction times, impaired judgment, and problems responding to signals and sounds on the road.

What happens when cannabis hits the brain?


Scientists recently discovered that one area of the brain that has several THC receptors is the memory center – the hippocampus. The hippocampus is the part of the brain in charge of certain types of learning and memory. That is how your teen can remember today's lessons or a new friend's phone number.

I said hippocampus not hippopotamus!

Disrupting the normal functioning of this memory center can lead to trouble studying and learning, and problems recalling recent events. The difficulty can be a lot more serious than "Did I take out the trash this morning?" Under the influence of cannabis, new information may never register - and may be lost from memory.


Cannabis also affects emotions. Maybe you've heard that in some people cannabis may cause uncontrollable laughter one minute and paranoia the next. That's because cannabis also influences emotions, probably by acting on a region of the brain called the limbic system.

Medical Dangers

The list of negative effects of cannabis goes on and on:

Puff for puff, smoking cannabis may increase the risk of cancer even more than smoking cigarettes does.

Where does cannabis come from?

Cannabis is grown all over the world; in fields as a crop or inside buildings - as long as there is water and artificial light. Different weather and soil conditions can change the amounts of the chemicals inside the plant, which means that certain parts of the world produce stronger cannabis than others.

How is it used?

Cannabis is used in many ways: Marijuana and hashish can be smoked in cigarette-form, as blunts (cigars hollowed out and filled with the drug), or smoked through a water pipe called a bong or a hookah. Hashish is sometimes placed between two heated knife blades, and then users inhale the resulting smoke. Hash oil is added to marijuana or tobacco cigarettes. Some users brew marijuana as tea or mix it with food.

The most common method is smoking loose cannabis rolled into a cigarette called a joint or nail.

Cannabis: "Everybody's doing it!"

No, it’s not true that everyone is using, even if your teen seems convinced this is true.

Everyone is doing it... well, at least one of them in my class... school... in fact, I'm not really sure who does it!

The World Health Organization conducted a study of youth from 35 different countries and regions. According to this piece of research cannabis use varies widely among 15 year olds in different countries: those who have ever used it range from 3% to 46%. Further, on average boys are more likely to have tried cannabis (22%) than girls (16%).

A recent survey in the US showed that only 8.3% of 13-14 yr olds, 17.8% of 15-16 yr olds and just 21.5% of 17-18 yr olds had used the drug in the past month.

Many parents are surprised to learn this – and so are teenagers!

Regular cannabis use (3 – 39 times in the previous month) is highest (15% or over) in Canada, Spain and Switzerland.

It may be true that some people use cannabis and apparently come to no harm and stop using as they grow older. Some continue to use with no “apparent effects”. However it is like Russian roulette – you can never be sure what impact it will have - or is having; when this will show; and how harmful the impact will be. It is even more likely to be problematic when used with other substances like alcohol or other drugs.

“It never did me any harm” may be easy for you to say – but your experience does not guarantee it will not cause your child harm.

What about medical marijuana?

Your teenager may argue that cannabis is a medical miracle, and should be legalized. In fact, many adults, political leaders and people in the media and entertainment industries are strong advocates for making it legal to grow and use cannabis for medical purposes.

THC, the main active ingredient in cannabis, does produce effects that potentially can be useful for treating a variety of medical conditions. It is the main ingredient in a synthetic pill that is currently used to treat nausea in cancer chemotherapy patients, and to stimulate appetite in patients with wasting due to AIDS. Scientists are continuing to investigate other potential medical uses for "cannabinoids".

Even though THC has been shown to contribute to improvement in some diseases and medical conditions, smoking cannabis is difficult to justify medically because the amount of THC in cannabis is not always consistent, and smoking is bad for one’s health. It would be difficult, if not impossible, to come up with a safe and effective way to smoke cannabis for medical purposes. The negative effects of any kind of smoke on the lungs offsets the helpfulness of smoked marijuana for some patients.

Medical use of marijuana under prescription and in controlled conditions may have its place as we learn more about how to use to offer more benefit than harm to some. But this is far from accepting the drug as something that should or could be used by everyone with no negative effects.

It is important to remember that prescription medicines are dangerous if used without supervision from a doctor.

Understanding a Cannabis-Like Drug: Spice

Smokable herbal mixtures under the brand name ‘Spice’ are known to have been sold on the Internet and in various specialised shops since at least 2006. Spice is advertised as an ‘exotic incense blend which releases a rich aroma’ and ‘not for human consumption’, and its chemical structure differs substantially from the active ingredient of cannabis (THC). However, when ‘Spice’ products are smoked, users report the effects similar to those of cannabis.

Other Drugs

Selection of drugs and alcohol

There are many other drugs that can be misused or abused. For more information on these please visit one of the sites below:

There is a colorful A to Z of drugs at Talk to Frank.

The Mentor POP Group has information about different drugs written for young people by young people.

NIDA has a chart that divides drugs gives into types: Depressants, dissociative anesthetics, hallucinogens, opioids and morphine derivatives, stimulants, and other drugs. They also provide pages on the various drugs.

Talking to Your Child About Drugs

Check the information on drugs and write down the things you read that you think are really important to share with your child.

Now plan how and when you will share this information with them. Plan your responses to statements like:

  1. But it is fun to try cannabis. I won’t use it a lot. Just for fun with my mates.
  2. Everyone else does it and they don’t come to any harm.

What You Need to Know About Cannabis

We have focused on cannabis in this chapter as it is the most commonly used illegal substance by young people and one which they are likely to come across and be offered. The prevention-smart parent needs to be aware of the risks and potential harm this substance can cause and try to discuss this with their child. It is no good being alarmist as the children will often point to their experience of people they know who use cannabis with no apparent negative effects but hear of the pleasant and soothing influence it can have. They will often argue it is less dangerous than alcohol and tobacco. However they need to know it is a risk to use it, as well as being illegal and that the consequences of use, particularly regular use of skunk and a mix of drugs used can have very harmful consequences that can ruin lives.

Information about drugs is useful but never enough on its own. The chapter offers websites that give lots of information on drugs for you and your children.

The important thing is how we use the information we have. Just telling your children the facts will not necessarily effect how they behave with respect to these substances. The prevention-smart parent has to think how to give or share the information in a way that is well received by their child and also look at the other reasons that may result in their child using drugs. We look at these “causes” or “contributory factors” towards drug use in Chapter 7: How Do I Protect My Child From Drugs?

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