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Cannabis is the most widely consumed psychoactive drug in the UK after alcohol and is particularly popular with teenagers seeking to experience effects such as relaxation and pleasure.

These positive effects have been sought after for centuries and initially, cannabis was consumed for its medicinal qualities, but as these effects became widely known more people started to take the drug recreationally.

Cannabis is a drug that originates from a plant called Cannabis Sativa and tends to be available in 3 forms in the UK: resin, marijuana and sinsemilla (including skunk).

These three varieties consist of different chemical components with their main ingredient THC more potent in some forms than others.

THC is the main psychoactive element in cannabis and is responsible for the high” sensations people experience when consuming the drug.

Psychological Effects Of Taking Cannabis

Mental Health

Alongside feelings of pleasure and relaxation, people taking cannabis may also find their perception of time is altered and their sensory experiences can be different from what they are accustomed to.

Some cannabis users claim they have an enhanced potential for creativity after taking the drug, hence its use by artists and musicians.

Cannabis’ effects are almost immediate and can last for up to 4 hours depending on how much has been taken.

Cannabis is considered less harmful than other drugs and whilst people can become psychologically dependent on it, the effects are nowhere near as harmful as opioid drugs.

Anxiety and brain

Even so, consuming cannabis for a prolonged period can adversely affect a person’s cognitive abilities and mental health.

People who take cannabis are vulnerable to developing a sense of depersonalisation, where they become detached from themselves and the world around them

Medical studies have shown that cannabis can cause temporary psychosis, a symptom of Schizophrenia.

What Is Schizophrenia?

Schizophrenia is a severe, chronic mental health condition that can have a debilitating effect on those diagnosed with it, as it tends to be associated with unpleasant and upsetting symptoms.

It can be a difficult condition to diagnose because of the wide range of symptoms that people with the condition exhibit, and not everyone diagnosed with the condition will show exactly the same symptoms.

Symptoms Of Schizophrenia

Different effects

One of the main symptoms of schizophrenia is visual and auditory hallucinations, where people will see images or hear sounds that are not actually present.

Anyone diagnosed with schizophrenia may suffer from delusions based on inaccurate beliefs about themselves and the way the world is.

They may have muddled and confused thought processes, display poor reasoning abilities, and can appear to have lost any enthusiasm to complete daily tasks.

man headache

They may for example forget about washing themselves and neglect aspects of their self-care.

Psychosis is another medical symptom that is associated with people diagnosed with schizophrenia.

This means they may appear to have lost touch with reality and lost the ability to separate their own beliefs, views and feelings from the world around them.

It may also be apparent that they begin to have problems with their speech and language, they may talk in an incoherent way.

There is also a tendency in those diagnosed with schizophrenia to withdraw themselves from their social world and lose their motivation to maintain contact with their friends.

Cannabis Use And The Risk Of Schizophrenia


Research over the years has consistently shown that consuming cannabis can lead to temporary psychosis.

A person can be judged to be in a state of psychosis when they seem to have lost touch with reality and experience hallucinations, appear delusional in the comments that they make, have disturbing thoughts and exhibit a confused state of mind.

Certain individuals (mainly young men) are vulnerable to exhibiting symptoms indicating a psychotic illness after consuming cannabis.

Research findings suggest that nearly half of all individuals who required treatment for cannabis-related psychosis went on to be diagnosed with schizophrenia in the future.

cannabis plant

Many researchers have felt that cannabis does contribute to the development of schizophrenia, as studies have revealed that any individual who smokes cannabis early on in adolescence is more likely to be diagnosed with schizophrenia than those individuals who do not consume the drug.

Any adolescents who have already received a diagnosis for a mental health condition will find they are more likely to develop symptoms associated with schizophrenia.

Likewise, symptoms associated with their current condition are likely to be made worse.

Cannabis-Related Cognitive Deficiencies And Schizophrenia

Man depressed

Taking cannabis can lead to problems with:

  • Attention
  • Short-term memory recall
  • Verbal memory
  • Concentration
  • Planning
  • Problem-solving tasks

These difficulties play a role in the development of psychotic symptoms.

However, because there are a wide range of symptoms that cause schizophrenia unless a person has a full medical diagnosis, they may not actually have schizophrenia despite displaying some of the symptoms after consuming cannabis.

Diagnosis Of Schizophrenia


It must be stressed that there is a wide range of symptoms associated with a clinical diagnosis of schizophrenia.

Not everyone who has received a diagnosis of schizophrenia will have exactly the same symptoms due to the nature of the diagnostic process.

The Potency Of Cannabis

cannabis plant

One factor worth mentioning when assessing whether consuming cannabis leads to psychotic symptoms is the potency of the drug.

It is important to understand that cannabis is a broader term that encapsulates cannabis resin, marijuana and sinsemilla (including skunk).

These three types of drugs are all chemically dissimilar with different combinations of chemicals and contain varying amounts of its vital constituent, THC.

smoking cannabis

There tend to be low levels of THC in cannabis resin but high levels in skunk.

Research findings suggest that separate types of cannabis affect people’s mental health differently, and some individuals will have a genetic vulnerability to specific forms of cannabis, mainly those with higher levels of THC present.


CBD oil

Researchers exploring the link between cannabis and schizophrenia propose that the level of THC in the form of cannabis being consumed is the most significant factor in determining whether cannabis is likely to have a therapeutic or damaging effect on the person taking the drug.

Individuals who smoke cannabis consisting of higher levels of THC which is found in skunk are more prone to developing the psychotic symptoms associated with schizophrenia, whereas those who consume cannabis resin which contains a higher level of CDB are more likely to experience therapeutic effects.

Cannabis Use In Adolescence

Many epidemiological studies (studies that investigate cause and effect) have found that smoking cannabis during adolescence substantially increases the risk of developing schizophrenia later on in adulthood.

Those that smoked greater amounts, and those who smoked cannabis earlier in adolescence were more likely to develop schizophrenia.

A study conducted in Holland in 2002 found that 50% of cannabis users who did not have symptoms of schizophrenia before smoking cannabis developed symptoms after using cannabis.

Cannabis And Neurological Development

cannabis bud

Many teenagers initially experiment with cannabis as they progress towards adulthood.

Academics believe that the link between cannabis consumption and schizophrenia is apparent because the adolescent brain is still in a critical period of development during adolescence.

Regular consumption of a psychoactive drug during this stage of their development could affect a person’s neurological development and psychotic symptoms could be a consequence of the way THC affects the developing brain.

Models Of Explanation

doctor with notepad

Researchers have developed three models to help explain the relationship between cannabis use and the psychotic symptoms associated with schizophrenia.

These are:

  • Vulnerability Model – Certain individuals are prone to developing schizophrenia if they smoke cannabis because of a genetic component in their neurological and psychological structure. They may also be at risk if a family member has also been diagnosed with the condition. People with certain vulnerabilities can also experience severe symptoms and are at risk of relapsing back after a period of good health. It has also been noted in research that some individuals can be affected by some types of cannabis and not others.
  • Symptom Alleviation – This model proposes that individuals with forms of psychosis whether it is diagnosed or undiagnosed use cannabis because they know it will alleviate the negative symptoms they are experiencing. It is uncertain whether cannabis use preceded or followed by the psychotic symptoms associated with schizophrenia.
  • Common Factors – According to this model people who take cannabis and have psychotic symptoms share certain things in common, such as genetic vulnerability, other co-occurring conditions such as anti-social personality disorder, and share similar lifestyle habits.

Research has indicated that certain personality traits such as neuroticism and impulsivity can be associated with people who are vulnerable to being diagnosed with schizophrenia after taking cannabis.


Group therapy - teens - black and white

There are many biological, psychological and social factors that need to be considered when examining the relationship between cannabis and schizophrenia, and it is difficult to establish any certainties about whether they have a causal relationship.

What can be established though is that consuming cannabis during adolescence can lead to a diagnosis of schizophrenia if someone has a genetic vulnerability to developing the condition.

The younger the person consumes the drug, the greater the risk.

Not all forms of cannabis are the same – medical researchers have put forward that THC is the key component in triggering psychosis.

Group therapy - hands in air

The greater the amount of cannabis containing THC a person smokes the greater the likelihood of them developing cognitive difficulties, poor mental health and the psychotic symptoms associated with schizophrenia.

If you are concerned about your cannabis use and the effect it has on your mental health, or about any other addiction you may be suffering from, contact Rehab 4 Addiction today.

We are here to help you every step of the way.