The Link Between Cannabis and Schizophrenia

Although cannabis has been used by humanity for centuries, the impact it has on the brains of younger people is often neglected. In the following article, we're going to explore further.

Written and verified by the psychologist Valeria Sabater.

Last update: 25 August, 2024

Is there a link between cannabis and schizophrenia? You may well have heard that marijuana or its psychoactive, THC, lies behind this serious mental illness. So, firstly, we must clarify that this depressant drug doesn’t generate schizophrenia on its own. However, it can activate the illness in those who already possess a genetic predisposition to it.

Cannabis is one of the most widely used psychoactive substances among adolescents and young adults. Persistent use in people with immature and developing brains can present worrisome risks and side effects.

Although cannabis is a compound with a long tradition in our cultures, and its administration is legal in some countries, it’s important to understand its contraindications.

Cannabis

Cannabis or marijuana can come from any of three plants with psychoactive properties: Cannabis sativa, Cannabis indica, and Cannabis ruderalis. When its leaves, stems or flowers are dried, it’s consumed for its relaxing effects. This explains its recreational and medical usage.

It’s interesting to know that cannabis contains more than 120 components, known as cannabinoids. But, science still doesn’t know the functionality or effects of them all. In fact, up until now, the pharmaceutical industries have focused their interest on only two key substances. They’re as follows:

• Tetrahydrocannabinol (THC). This is the main psychoactive in cannabis. It’s responsible for the classic ‘high’, due to the stimulation it generates in neurons to release dopamine.
• CBD. This is used to relieve inflammation and pain. However, a study published in the journal, Neuropsychopharmacology argues that the mechanisms of CBD are still not fully understood. Therefore, more research is required regarding the substance.

The effects of marijuana

Cannabis is considered to be a ‘harmless’ drug with rewarding relaxing effects. That said, science has doubted its apparent harmlessness for decades. A study published in the journal, Stroke focuses on those who use this substance the most: young people.

In the case of prolonged consumption, marijuana has an extremely harmful impact on the brain. Here’s how the body and mind react to its effects.

Short term effects

• Dizziness.
• Relaxation.
• Pain relief.
• Sense of well-being.
• Increased creativity.
• Altered sensory perception.
• Variation of space-time perception.

Long-term effects

• Nausea.
• Lethargy.
• Irritability.
• Bronchodilation.
• Sleeping problems.
• Memory problems.
• Psychotic episodes.
• Increased anxiety.
• Alterations in attention.
• Reduced blood pressure.
• Increased aggressiveness.
• Slower reaction times.
• Difficulties processing information.
• Acute and chronic adverse effects can appear both in physical and mental health. This is confirmed in an investigation conducted by Hospital de Sant Pau, Barcelona (Spain).
• Cannabis or marijuana can become an addictive drug. A study published in the Journal of Neuroimmune Pharmacology indicates that the neurobiological changes of this substance are similar to other addictions, although with less cerebral impact.

Cannabis and schizophrenia: uses and risks

Cannabis and schizophrenia are of great interest to the fields of psychology, psychiatry, and neuroscience. Indeed, the idea that persistent use of cannabis acts as a trigger for this mental illness is often reinforced.

As we mentioned earlier, marijuana can be dangerous if the individual already has a genetic predisposition toward schizophrenia.

Cannabis and schizophrenia in men

Cannabis use is a proven risk factor for young people between the ages of 16 and 25. Some recent studies, such as those published in the journal, Psychological Medicine, provide significant information that should be taken into account, particularly when it comes to countries’ marijuana legalization processes.

This research was conducted with 6,907,859 individuals. It states that one-fifth of the cases of schizophrenia among young men could be prevented by avoiding cannabis use.

• Marijuana use is especially significant among young males. They develop schizophrenia to a greater degree if they possess a genetic predisposition to the illness.
• Cannabis use disorder has risen in recent years. This is a risk factor for the number of patients with schizophrenia to also rise since THC acts as a trigger for the illness.
• THC can trigger and/or worsen schizophrenia if the patient has already developed it. As a rule, this psychiatric disorder first exhibits its symptoms between the ages of 18 and 25.

Why do people with schizophrenia use cannabis?

It’s extremely common for patients diagnosed with schizophrenia to smoke marijuana for its relaxing effects. Many people report feeling more centered, with a greater sense of well-being and inner calm. This perception also makes them believe that thanks to cannabis, their psychotic episodes will be reduced.

However, the scientific community has already established, via various studies, that this perception is wrong. Since cannabis compounds are an element of great interest to the pharmaceutical industry, their therapeutic use in schizophrenia sufferers has been investigated.

In fact, there’s still no conclusive evidence that cannabis has a positive benefit on the symptoms and cognition of people with schizophrenia (Ahmed et al. 2021). More studies are required; those that focus on better analyzing the doses, form of administration, and characteristics of the patients.

Cannabis as psychedelic therapy

Now you know the link between cannabis and schizophrenia and are aware of the risk of continued use of this psychoactive drug. But, what about its therapeutic use? Indeed, it’s true that many patients with chronic pain or who are undergoing chemotherapy benefit from the administration of marijuana.

Furthermore, in recent years, cannabis has formed part of psychedelic therapy, like MDMA, psilocybin, and ayahuasca. These are therapeutic models assisted by specialists, in which the patient is, at all times, in a controlled clinical context.

To address cases of trauma or post-traumatic stress, the administration of cannabis starts with specific microdoses, A study published in the journal, Frontiers in Psychiatry describes the benefits in one particular case history. It also highlights the need to increase examinations in this field, especially in more serious cases such as complex trauma. We await further progress in this regard.