Cannabis (marijuana, hashish, pot) is a drug derived from the female hemp plant (Cannabis sativa or Cannabis indica). It contains more than 100 substances known as cannabinoids, including THC. Marijuana (weed) is produced from the dried, greenish-brown flowering tops of the plant. Hashish or hash may be produced in various ways; usually that involves sifting the resin secreted by the tops and compressing it into blocks.

Mode of use

Marijuana and hash can be smoked, vaporised, or swallowed in solid or liquid form. Smoking is the most common technique.


In the Netherlands, cannabis is usually rolled with tobacco into a joint, but it may also be smoked on its own in a small pipe or in a water pipe called a bong. A bong filters out more THC than tar, and therefore delivers no health gains; it does cool off the smoke. Hash oil is a thick, dark liquid. It is usually dabbed or smeared onto a rolling paper, which is then smoked as a joint with ordinary tobacco; the oil may also be dripped onto the tobacco itself before rolling.

Unity tip If you want to smoke pot, smoke it without tobacco. Better still, don’t smoke it at all. Try a different technique like a vaporiser to avoid getting toxic substances into your lungs.


Vaporising (vaping) is less harmful than smoking. A vaporiser heats up the marijuana or hash, rather than burning it. At a temperature of 180° to 200° C, only the active substances are released, so you inhale no nicotine, tar or carbon monoxide.

Eating or drinking

Cannabis can be eaten or drunk after being blended into other refreshments like tea, space cake or hash sweets. Such ‘cannabis edibles’ often produce unpredictable effects. It might even take 1 to 2 hours before you feel any effects at all. Effects may also last longer than when cannabis is smoked. This can turn into a distressing experience, especially for people who don’t know what to expect.


The substance that makes you high or stoned is THC (delta-9-tetrahydrocannabinol). The more THC that your marijuana or hash contains, the stronger it will be. Another natural ingredient of cannabis is CBD. It does not make you stoned, but it influences the effects of THC. It is possible that CBD (and especially the ratio of CBD to THC) can counteract some of THC’s effects, such as acute psychotic symptoms, anxiety, poor memory or reward sensations.

It is difficult to find the right dose of cannabis, because the strength and the ratios of THC and CBD vary greatly. Dutch-produced marijuana, or skunk, contains almost no CBD at all; foreign-produced hash often does contain CBD. The effects of cannabis may vary between feeling trippy, high or stoned, depending in part on the relative strengths of THC, CBD and other cannabinoids. One gram of hashish or marijuana is usually enough to roll 4 to 5 joints.

Effects of cannabis

How you experience the effects of cannabis depends on three things:

  1. Set − Who you are, what you’re expecting and how you’re feeling
  2. Setting − Where you are; a lively party or quiet at home.
  3. Drug − What drug(s) you are taking and in what amounts.

Positive effects

  • carefree, relaxed, cheerful mood
  • intensification of feelings
  • more intense awareness of senses (sight, hearing, smell, touch, taste): music sounds more intense, food tastes better, physical contact feels more pleasing
  • giggles or uncontrollable laughter
  • stronger appetite (‘munchies’), particularly for sweets
  • pain relief.

Unity tip You can get paranoid and fearful from taking cannabis. Set and setting therefore play an important role. Don’t consume cannabis unless you are feeling good and are in a pleasant situation around people you feel comfortable with. And know your own limits.

Negative effects

  • heavy arms and legs
  • dizziness and nausea, especially in combination with alcohol
  • fatigue, drowsiness, sluggishness
  • coughing, asthma attacks, irritated airways
  • impaired short-term memory functioning, forgetting things that have just happened, losing track during conversations
  • difficulty concentrating and thinking logically
  • elevated heart rate, palpitations
  • reduced blood pressure, especially noticeable if you stand up quickly (risk of fainting)
  • headache
  • confusion and clumsiness
  • anxious or paranoid feelings
  • intensified appetite (‘munchies’, binge eating), particularly for sweets
  • bloodshot eyes
  • dry mouth
  • distorted sense of time; time seems to move slowly
  • at high doses: introversion, hallucinogenic effects, panic attacks, nausea and vomiting.

High versus stoned

Cannabis can make you feel relaxed, woozy and sluggish (‘stoned’) or it can trigger lively fantasies and make you jovial (‘high’). This varies between different individuals and it may also depend on set and setting and on the type of cannabis you take.

Unity tip Holding the smoke longer in your lungs serves no purpose! Virtually all the THC is absorbed within seconds from your lungs into your blood. Holding in the smoke won’t get you higher or more stoned, but it will lengthen your exposure to toxic substances.

Freaking out

Freaking out means you get very anxious, go into a panic, feel sick to your stomach, hallucinate or even get seriously disoriented (freaking or flipping out). That can be a frightful experience.

You run a greater risk of freaking out if you

  • consume high doses of cannabis
  • are unfamiliar with its effects
  • feel moody or fatigued beforehand
  • swallow cannabis (space cake or other edibles).

Duration of effects

If you smoke pot, you perceive the initial effects within a few minutes. The effects last 2 to 3 hours and then gradually diminish. After 5 to 6 hours, users normally feel reasonably sober again. In some cases, as when cannabis is eaten, effects can persist for up to 12 hours. We therefore advise inexperienced users not to eat cannabis, in view of the unpredictable effects.


After moderate use of cannabis, the drug may be detectable in your urine for one week. After prolonged use, detectability may increase to a month or more. That is because THC binds to fat tissues and is then released into the blood very slowly.

Short-term risks

The most common acute risks from cannabis use are:

  • severe dizziness and nausea
  • passing out
  • acute shortness of breath (bronchitis)
  • cannabis psychosis.

THC does not affect the brain areas that regulate heartbeat and breathing. That makes it almost impossible to die of a cannabis overdose.

CAUTION! Everybody is different, and we all react differently to drugs. Fortunately, serious health emergencies caused by cannabis are uncommon. Some people experience adverse effects from low doses, whilst less sensitive people feel no effects at all from the same dose. The risk of health problems depends on the strength and chemical composition of the drugs and on the sensitivity, health and behaviour of the user. The surrounding environment is also a factor. How many and what beverages have been consumed? How much exercise does the user get? How hot are the surroundings? Has the user taken different drugs in combination?


On the morning after a night of cannabis use, you may find it more difficult to get out of bed and pay attention to things. So it is never a good idea to smoke pot when you know you have to get up early, go to school or report to work the next morning.

Emergency care

A person under the influence of cannabis may start to have suspicious or fearful thoughts. Try to comfort them, give them something sweet to drink or eat and accompany them to a quiet place, preferably where there is fresh air. If they do not start to feel better and you are worried about them, take them to a first aid post or emergency department (Spoedeisende Hulp) or phone 112. Never leave a person alone who feels unwell.

Be honest about drugs. Medical staff are there to help. What you tell them is confidential. You will not get fined or prosecuted for drug use in the Netherlands.

Unity tip If you decide to take cannabis, do so only for recreational purposes and only if you are healthy and are feeling great beforehand. Don’t use cannabis if you have diabetes, a heart condition, issues with blood pressure, epilepsy or mental health problems. Don’t use cannabis if you are pregnant or are taking any medicines.

Combining cannabis with other drugs

Combining different drugs carries extra risks. It produces unpredictable effects and there is a greater chance of health problems.


Alcohol increases the risk of nausea and vomiting. The way you feel on this combination is also called ‘crunked’ or ‘twisted’. Most users don’t feel like drinking much alcohol after taking cannabis.

Speed, 4-FA, ecstasy, MDMA

Soe users enjoy the combination of cannabis with stimulants like speed, 4-FA or ecstasy (MDMA). Some claim that taking cannabis prolongs the effects of ecstasy, whilst others claim it tones down the ecstasy high. Still others perceive no effects of cannabis on ecstasy.


Cannabis taken in combination with hallucinogenic drugs can produce longer and more intense trips. Anxiety attacks and thought loops become more likely. Some people report that, while on cannabis, they have re-experienced hallucinogenic effects from earlier trips, and that this could be very scary and disorienting. If you have such experiences, we advise you to stop using cannabis.


Cannabis can get you into a mellow mood. You may feel less inhibited and your body may be more sensitive to contact with other people. But heavy cannabis use over the longer term can dampen your sexual desires. The effects of cannabis vary per individual person, and they also depend strongly on atmosphere and surroundings.

Unity tip Be sure you have condoms with you. Before taking drugs, agree with the person you’re with (or with yourself) about sexual contact. Set your limits.

Long-term risks

The more cannabis you take, the more often you take it, and the younger you are when you start, the greater your risk of developing problems. The most common problems over the long term are as follow:

  • slow or lagging personal growth
  • fatigue
  • poorer concentration
  • weakened physical condition and resistance
  • chronic bronchitis
  • impaired lung immune system
  • possible higher risk of lung cancer
  • greater risk of psychotic symptoms, particularly in individuals with a predisposition for them

Risks to your lungs

The smoke emitted by burning cannabis contains 3 times more tar and 5 times more carbon monoxide that tobacco smoke. It is therefore more toxic. One joint causes about as much harm as four ordinary cigarettes. ‘Passive pot smoking’ is also harmful. Heavy pot smoking increases your risk of chronic bronchitis and chronic cough. The combination of tobacco and cannabis puts a double or worse strain on your lungs. Some research studies suggest that prolonged, frequent pot smoking leads to an elevated risk of cancers of the mouth, throat, oesophagus and lungs. Some of these risks can be reduced by using a cannabis vaporiser.

Risks to your brain

Cannabis affects the functioning of the brain. Such effects are nearly always temporary. According to the current state of knowledge, the limited use of cannabis has no lasting effects on brain functioning and causes no permanent damage to brain areas. Chronic effects are seen only in people with early-onset cannabis use and in long-term heavy users.

Cannabis and psychosis

Cannabis psychosis

Cannabis consumption, especially in high doses, is known to increase the risk of ‘cannabis psychosis’. You lose touch with reality, and you may experience anxiety, confused thought or speech, hallucinations and delusions. The difference between cannabis-induced psychosis and other types of psychosis is that the former resolves after the effects of the THC wear off; other psychoses may recur or continue when you are not under the influence of cannabis.

Mental health problems

It has been known for some time that mental health disorders can be exacerbated by cannabis. In individuals who are predisposed to psychosis, the use of cannabis may trigger or intensify psychotic symptoms. The younger you are, the more cannabis you take, and the more often you take it, the greater your risk of experiencing psychosis or other problems with thinking, memory or concentration.


Unity tip One of the risks of using cannabis is that psychological problems you already have may worsen. If you have ever started to feel suspicious of other people after taking marijuana or hash, or if you know you have a predisposition to develop psychosis (as when members of your family have had psychotic experiences), then we strongly advise against taking cannabis.


Approximately 1 in 10 cannabis users sometimes experience addiction symptoms. They may develop a tolerance for cannabis, whereby they need to consume greater amounts to achieve the desired effects. Heavy users of cannabis may experience withdrawal symptoms if they stop taking the drug; these may persist for up to 2 weeks. Withdrawal systems include

  • nervous unrest, irritability
  • sweating
  • shaking
  • headache
  • anxiety
  • insomnia

Unity tip Symptoms like the above may make it difficult to stop taking cannabis. Additional information and low-threshold assistance is available via the internet or via a doctor’s practice.

The law

Cannabis is classed in schedule 2 of the Dutch Opium Act. Possession, production, trade, transport, import and export are all punishable by law. The use of cannabis is not punishable. The possession of up to 5 grams of cannabis or up to 5 cannabis plants for personal use is currently not prosecuted in the Netherlands, but the drugs may still be liable to confiscation. Growing cannabis in rented premises may be explicitly prohibited in tenants’ contracts and may constitute grounds for eviction. Hash oil is classed in schedule 1 of the Opium Act.

Unity tip Cannabis slows your reaction time, your coordination and your concentration. If you must drive or cycle, avoid taking cannabis for at least 4 hours beforehand.

Taking cannabis is never without risk! By carefully reading the information and advice in this leaflet and heeding the tips provided by Unity, you can limit the side-effects and health risks from cannabis as much as possible.