Cannabis Induced Psychosis

Can Weed Cause Psychotic Symptoms?

Cannabis is a commonly used recreational drug. It is popular because it causes effects that some people find pleasurable.

Unfortunately, like all recreational drugs, it also causes many unpleasant side effects. One of the most distressing side effects cannabis can cause is cannabis-induced psychosis.

What is Cannabis?

Cannabis, also known as marijuana or weed, is the most commonly used illegal drug. It is especially popular with teenagers and young adults. It is made from the cannabis plant and is usually smoked, although it can be eaten.

Cannabis contains Tetrahydrocannabinol

Cannabis contains a chemical called tetrahydrocannabinol (THC). THC is a psychoactive compound that affects mood and behaviour. The concentration of THC determines how intense the effects of cannabis are. Over the years, the concentration of THC in cannabis has increased.1 A lot of the cannabis available nowadays has high levels of THC, making it highly potent. The effects people experience from high-potency cannabis are much more extreme.

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Why Do People Use Cannabis?

Cannabis causes a range of effects that people can find pleasurable, which is why it’s so commonly used. People usually refer to these effects as being “high”.

Cannabis can:

  • Increase feelings of relaxation
  • Make you feel more social
  • Alter time perception
  • Make things seem funnier
  • Change the way you interpret sensations 

Side Effects of Cannabis

Unfortunately, cannabis can also cause a range of unpleasant and harmful effects. 

Some of the most common side effects of cannabis use include:

  • Anxiety and panic/Nausea (feeling sick)
  • Confusion/Dry mouth/Watery eyes
  • Racing heart
  • Derealisation (feeling as if things or people around you aren’t real)
  • Memory difficulties
  • Worsening of mental health problems
  • Cannabis psychosis

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What is Cannabis Intoxication?

Cannabis intoxication refers to significant psychological or physical symptoms that develop following cannabis use. These symptoms can be either pleasant or unpleasant as described above. Cannabis intoxication develops minutes after smoking cannabis, and several hours after eating it. 

In some cases of cannabis intoxication, people can experience psychotic symptoms like hallucinations or delusions.

Cannabis Psychosis

Cannabis use is linked to psychosis. Cannabis use significantly increases the risk of having a psychotic experience.

It’s important to remember that the development of cannabis psychosis is complex. Not everyone who uses cannabis will experience cannabis-induced psychosis. It is likely that there are many factors that determine whether or not someone develops psychosis from cannabis use. These factors include other health conditions, genetics, and environmental factors.

What is Cannabis Psychosis?

Psychosis is a medical term used to describe when someone loses contact with reality. It can occur as a symptom of physical and mental health problems or as a side effect of drugs. When psychosis occurs as a result of cannabis use it is known as cannabis-induced psychosis or cannabis psychosis.

When someone experiences psychosis, they interpret reality differently from others around them. In cannabis psychosis, people usually experience three main groups of symptoms:

  • Delusions

This is when someone has a belief that is not shared by others. Delusions in psychosis are usually unpleasant and based on paranoia. For example, they may believe that the government has installed cameras in their mirrors, or that people in the street are plotting to hurt them.

  • Hallucinations

This is when someone sees, hears, feels, smells, or tastes something that is not really there. For example, someone with psychosis might hear voices or see people or objects that aren’t really there. They might feel someone grabbing them when no one is there, or smell or taste something that does not exist.

  • Confusion

People experiencing psychosis are often confused. They may speak rapidly, changing topics frequently and losing track of what they are saying.

Cannabis-induced psychosis can be incredibly scary. People can feel completely detached from reality, anxious, and unsure of who to trust.

Is Cannabis-Induced Psychosis Dangerous?

Yes, cannabis psychosis can be extremely dangerous. The psychosis itself does not cause harm, but the delusions and hallucinations experienced can convince people that they need to do dangerous things. During psychotic episodes, people may take actions that put their safety and the safety of others at risk.

For example, someone experiencing cannabis-induced psychosis might hear voices telling them they need to jump out a window. If they were to do this they could injure or even kill themselves. An episode of psychosis could convince someone that people are plotting to hurt them, and they may take measures to “defend” themselves such as hurting others.

If someone is experiencing cannabis-induced psychosis they should receive urgent medical attention. 

How Is Cannabis-Induced Psychosis Diagnosed?

To make a diagnosis of cannabis-induced psychosis your doctor will need to:

  1. Witness or hear a history of delusions or hallucinations
  2. Obtain a recent history of cannabis use and how this correlates with your onset of symptoms
  3. Rule out other causes of psychosis

What Are the Other Causes of Psychosis?

Psychosis is not a mental health condition, but rather a presentation of physical and mental health problems. Some of the problems that can lead to psychosis are:

  • Mental health conditions

Certain mental health problems can lead to psychosis, including Bipolar Disorder, Schizophrenia, and severe Depression or Anxiety.

  • Physical health problems

Health conditions that affect the brain can cause psychosis, including conditions such as HIV/AIDs, Syphilis, and brain tumours.

  • Trauma and stress

Traumatic life experiences and severe stress can trigger psychotic episodes.

  • Recreational drugs

In addition to cannabis, many recreational drugs can trigger psychosis including, cocaine, ketamine, MDMA, LSD, and amphetamines.

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What Should You Do if Someone Has Cannabis-Induced Psychosis?

If you’re worried someone has cannabis-induced psychosis you should try to get them medical help. 

Remember that keeping yourself safe is a priority. If you’re worried that the person is an immediate risk to themselves or others you should call 999 for an ambulance.

  • Stop them from ingesting/smoking further cannabis

Remove the cannabis joint or edibles to stop them from taking more, and open windows to ventilate the area and clear the cannabis from the air. 

  • Reassure them

Listen to their concerns, and explain to them that they are safe and that you will get them help. Remember that the hallucinations and delusions they are experiencing may seem so real it may not be possible to reassure them.

  • Get professional help

Contact your local medical services to get the person the appropriate help they need. Remember, if they are an immediate threat to the safety of yourself or others you should call 999.]

Can You Get Addicted to Cannabis?

Yes, it is possible to develop an addiction to cannabis. THC, the main psychoactive compound in cannabis, appears to be an addictive component. This is because it causes a range of effects on the brain, including increasing the release of the feel-good signalling molecule dopamine.

People with cannabis addiction will find themselves continuing to use cannabis despite the negative effects their use causes. They will also find themselves experiencing withdrawal symptoms when they go for periods of time without using. This is because their mind and body have become used to a certain level of the drug. 

Withdrawal symptoms can include:

  • Feeling nervous or anxious
  • Feeling angry or irritable
  • Aggression/Low mood/Difficulty sleeping
  • Tremors, Sweating
  • Fever/chills
  • Headache 

Thank you for looking after Lewis during his time with you at Castle Craig. The day I dropped him off you promised that you would look after my son – and you certainly did that. After many years I now have Lewis back and I can’t tell you just how amazing that is!!! Lewis continues to do well and is a joy to be around. The work you do is incredible and really does save lives.

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Support for Cannabis Addiction

If you or your loved one is struggling with cannabis addiction please know that help is available.

Castle Craig is one of the UK’s leading treatment centres, with over 30 years of experience in treating addictions. We offer cannabis addiction treatment in a safe setting with a multidisciplinary team of psychiatrists, nurses and therapists. Our programmes incorporate a range of evidence-based approaches, including medical management, and individual and group therapy. We also offer a range of complementary therapies and activities which provide emotional and spiritual healing. These include drumming therapy, equine therapy, art, creative writing and mindfulness meditation.

We continue to support patients after they have completed their treatment with us by providing:

  • A two-year continuing care plan
  • Weekly group therapy sessions
  • Teletherapy
  • Helping them to engage with local Narcotics Anonymous groups


  1. Is there a link between marijuana use and psychiatric disorders? – National Institute on Drug Abuse
  2. Cannabis-Induced Psychosis: A Review – Psychiatric Times
  3. The contribution of cannabis use to variation in the incidence of psychotic disorder across Europe (EU-GEI): a multicentre case-control study – The Lancet
  4. Cannabis and psychosis: A father’s story – Rethink Mental Illness

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