NCPIC - National Cannabis Prevention and Information Centre

Cannabis and aggression

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Does smoking cannabis cause aggression?

The use of cannabis typically causes a sedative effect, making the drug less likely to cause violence in users than other substances such as alcohol and stimulants (e.g. amphetamines and cocaine).

However, sometimes when people use cannabis it can cause fear, anxiety, panic or paranoia, resulting in an aggressive outburst. For most people, however, once the effects of the drug wear off, their behaviour gradually improves.

Studies show that violence can occur more often among people who use cannabis regularly, rather than those who use it occasionally or not at all. It is a matter for current research as to why this is the case. It may be because people with violent tendencies can also have a range of other psychosocial problems and are therefore more likely to use cannabis. It is also important to remember that cannabis is part of the illegal drug market, increasing the chance of violence to occur in some social interactions.

Research also shows that cannabis users who commit aggressive acts usually have a history of violence before they start using the drug.

In addition, when people are withdrawing from cannabis they can be irritable, sometimes leading to abusive or aggressive behaviour.

Why do people become abusive or aggressive?

Using cannabis can produce strange behaviour and reactions in people when they are intoxicated. These reactions can be similar to psychosis and paranoia and because of this, cannabis users may experience the following:

  • confusion – they misunderstand what is going on or what someone has said or done
  • feeling threatened or frightened
  • paranoia – they hear voices or think that people are out to get them

When people stop using cannabis they may experience a variety of withdrawal symptoms including:

  • sleep disturbance
  • irritability
  • loss of appetite
  • nervousness
  • anxiety
  • restlessness
  • sweating

Experiencing any of these symptoms can make a person angry, which is an emotional response to feeling threatened or frustrated. Anger ranges from mild irritation to violent rage. Some people can express their anger in a controlled and constructive way while others lash out in an aggressive, uncontrolled way, either immediately or letting their feelings build up. This can lead to intimidating, violent or bullying behaviour, endangering them, other people and property.

How can you respond to threatening or violent behaviour?

The impact and the effects of violence on an individual can be profound and long-lasting, so doing all you can to prevent violence actually occurring is important.

The aim of calming someone down is not to prove them right or wrong, but to allow them to regain control of their behaviour without resorting to violence.

The best time to intervene is when a person is feeling anxious. Be supportive, empathic and stay neutral. Ask them what is wrong and try to calm them down. Move them to a quiet place and stay with them until the effects of cannabis wear off.

If a person's behaviour becomes aggressive, you could try the following tips to help calm them down:

  • before trying to intervene it is important to remember your own safety as well as the safety of the threatening person and all the people and things around them. If you think you can achieve a safe outcome for all, try to calm them down
  • try to get other people who don't need to be there to leave the area
  • even if you're scared and nervous, act calm. Use their name and talk in a soft, even tone –do not shout back at them. Have a relaxed posture and be non-confrontational
  • don't touch them
  • ask them “What's made you feel upset/angry?”
  • listen carefully and show empathy, acknowledging their concerns or frustrations without being patronising
  • let them know that you are here to help them. If there is something you can do for them, do it
  • give them time to express themselves. Don’t hurry them
  • keep them talking and ask open-ended questions
  • be truthful
  • help them set limits – “Come on mate, keep your voice down”
  • re-assess – is what you are doing working? If it's not try something different or get help
  • if they calm down, try to distract them with other topics of discussion
  • stay with them until they and others are safe
  • get them help if need be – accident and emergency, police, other friends
  • if there is nothing you can do, retreat and get help

After the effects of cannabis or cannabis withdrawal wear off, talk to them about what happened, how it affected you and those around you, and how this could be prevented in future.

How to help prevent aggressive and violent behaviour happening again

You can do things that may reduce the likelihood of this happening to them again. These may include the following:

  • suggest they avoid cannabis use
  • if they have a mental illness like depression, anxiety or schizophrenia, encourage them not to use cannabis or take any other drug, unless prescribed by a doctor
  • encourage them to seek help from their doctor or a counsellor about their cannabis use and/or anger issues
  • remind them of what happened last time they used cannabis
  • suggest they avoid bingeing or polydrug use (using more than one drug at the same time), or anything that will intensify the effects of cannabis
  • do other activities with them that don't involve drug use

For more information please see the factsheet ‘looking after a friend on cannabis’.

Factsheet published June 6, 2008. Updated October 1, 2011.