The connection between schizophrenia and marijuana is complex. Marijuana contains several different components, two of which have received much attention for their unique effect on the brain. While the main psychoactive ingredient in cannabis (THC) can trigger or exacerbate psychotic symptoms in people with schizophrenia, cannabidiol (CBD) may have therapeutic effects with antipsychotic, anxiolytic, and neuroprotective properties.
What Is Schizophrenia?
Schizophrenia is one of a number of mental disorders that include chronic psychotic symptoms, like hallucinations and delusions. Though it occurs in under 1% of the population worldwide, its burden on family and society at large is far-reaching, with the illness being among the top 15 leading causes of disability.1,2 Usually schizophrenia is diagnosed between late adolescence and early adulthood with the onset of psychotic symptoms. However, subtle signs and symptoms may emerge earlier in the form of negative and cognitive symptoms.
According to the DSM-5, a person with schizophrenia will exhibit at least two of the first five symptoms (with at least one being a positive symptom) for a period of one month or more:
- Delusions: distorted beliefs that–despite possibly having a kernel of truth–are not supported by the overwhelming evidence accessible to most other objective, non-psychotic observers.
- Hallucinations: sensory illusions, in any sensory modality, that can take the form of seeing, hearing, or tasting things that aren’t really there.
- Disorganized speech: speech that does not make logical sense or is incoherent, possibly including nonsense syllables; or, the repetition of the same word or phrase over and over. Speech disturbances may also manifest as a reduction in speech (alogia) or an increase in speech (pressured speech).
- Disorganized behavior: behavior that does not fit a given situation.
- Negative symptoms: absence of typical, common, or normal features that most individuals regularly exhibit, such as blunted affect (reduced emotional expression), anhedonia (reduced experience of pleasure), and asociality (reduced desire to interact with others).
- Cognitive symptoms: includes symptoms such as verbal fluency and memory impairment that are used by clinicians to distinguish schizophrenia from other disorders.
What is Marijuana?
Marijuana refers to the dried parts of the cannabis plant. The plant contains over 140 natural compounds called phytocannabinoids.3 Two major phytocannabinoids that have received a great deal of attention are THC (delta-9-tetrahydrocannabinol) and CBD (cannabidiol).
THC, the main psychoactive ingredient in cannabis, is best known for its psychotropic (mind-altering) properties, including euphoria, sedation, and intoxication. However, it also can lead to deleterious effects like psychotic symptoms, anxiety, and cognitive deficits that resemble those seen in schizophrenia.
Conversely, CBD produces calming effects in users, much unlike THC. Though much of the research distinguishing the effects of THC, CBD, and other cannabinoids is in an early stage, there is some evidence to suggest that both THC and CBD have anti-inflammatory, immunomodulatory, and anticonvulsant properties.1 Understanding the different ways marijuana can influence your brain health is critical, as this drug is gaining popularity as legalization advances through much of the US and abroad.
How Does Marijuana Affect the Brain?
Endogenous cannabinoids can be found throughout the human body and brain, and seem to regulate the action of other neurotransmitter systems (dopamine, serotonin, glutamate acetylcholine, GABA) in a complex way. THC works by binding to CB1 receptors in the endocannabinoid system, altering the communication of neurons in a way similar to that seen in schizophrenia. Brain regions that are involved in reward processing, memory, impulse control, and emotion are affected by schizophrenia and also by THC. The CBD component of cannabis does not seem to bind to the same receptors as THC, but does seem to modulate the activity related to them, and actually dampens THC’s effects.5
Link Between Schizophrenia & Marijuana
Individuals with schizophrenia are particularly vulnerable for developing substance use disorders, and they are three times more likely than non-clinical individuals to misuse drugs and alcohol.6 With cannabis, the heavier the use, the greater the risk of developing psychotic symptoms. Moreover, heavy cannabis users are four times more likely to develop schizophrenia or related psychotic disorders than non-users.7
Cannabis use often precedes the onset of schizophrenia with a gap of about seven-to-eight years (depending on severity of use) from the first use of cannabis to the onset of psychotic symptoms.7 It has been suggested that chronic use of marijuana gradually alters the brain circuitry, underlying both schizophrenia and addiction. Hence, cannabis use during adolescence is particularly concerning, as healthy brain development can be neurophysiologically derailed.
The THC component of cannabis can lead to transient psychosis in anyone consuming it, with the effect lasting anywhere from a few hours to a week. Between 20% and 50% of non-clinical cannabis users experience psychotic symptoms, such as paranoia, hallucinations, and delusions.8,9 Usually, a temporary cannabis-induced state of psychosis does not produce symptoms for long enough to warrant a diagnosis of cannabis-induced psychotic disorder. This is because these symptoms generally subside within 24 hours. Clinicians may diagnose these psychotic-like perceptual disturbances following cannabis use as cannabis intoxication.10
When the perceptual disturbances specifically take the form of hallucinations or delusions, or they are more severe (lasting upwards from a few days to several weeks), clinicians may diagnose cannabis-induced psychotic disorder (CIPD). However, a considerable percentage of CIPD patients (46%) go on to develop schizophrenia.10 Relatedly, genetics does seem to play a partial role in both cannabis-induced psychosis and schizophrenia.11
A cannabis-induced psychotic episode may include:
- Delusions: Persecutory delusions are the most common type, while grandiose delusions and delusions of reference are also reported.12
- Paranoia: Related to delusions, feelings of suspiciousness are fairly common in a cannabis-induced psychotic episode.
- Hallucinations: Visual and auditory hallucinations may occur, though visual hallucinations are more common when induced by cannabis.12
- Anxiety: While many cannabis users experience a calming effect, some may become more anxious.
- Blunted Affect: The expression of emotion may be reduced.
Can Cannabis Cause Schizophrenia?
The extent to which cannabis use causes schizophrenia or is merely correlated with it remains unclear, especially since numerous factors underlie both phenomena. Just as peanuts do not cause anaphylaxis in all people (only those with a severe peanut allergy), not all individuals who use cannabis develop schizophrenia. In fact, most cannabis users don’t develop the disease.
The absence of a clear, direct causal link does not eliminate cannabis use as a possible trigger for schizophrenia. Therefore, the link is likely indirect and mediated by other factors. These factors may include genetic vulnerability, neurological vulnerability, and various environmental/demographic risk factors. Even in the absence of substance use, it is believed that schizophrenia is caused by a combination of these contributors.
The degree of risk for cannabis to trigger schizophrenia also relates to the ratio of THC to CBD in the substance used. While the THC component in cannabis may trigger schizophrenia, CBD has been shown to have potential therapeutic and neuroprotective effects.
According to research, the use of cannabis (and particularly THC) in at-risk individuals may:
- Accelerate the onset of schizophrenia: The younger the age one starts using cannabis, the earlier the onset of psychotic symptoms in those who do develop schizophrenia. Heavy usage also influences this.13
- Increase the risk of developing a SUD: Some have suggested that the same vulnerability in brain circuitry (dopaminergic ‘reward circuit’) that can lead to schizophrenia may also lead to substance dependence and misuse.6
- Induce temporary psychotic symptoms: Individuals at risk for schizophrenia (as well as first time users) are more likely to experience psychotic symptoms than other users.11
- Affect learning and memory: THC in cannabis can impair the areas of the brain involved in learning and memory. Impaired functioning in these areas can cascade to a range of consequences, from diminishing performance in school or work, to reduced confidence. The younger the THC user, the greater the impact on cognition.
Does Marijuana Make Schizophrenia Symptoms Worse?
It has been suggested that some individuals with schizophrenia may use cannabis to self-medicate and reduce symptoms. Some research shows that many report using marijuana for the same reasons as non-clinical individuals do (i.e., intoxication, dysphoria relief, and relaxation).1 However, the relief of illness symptoms and medication side effects appears to be an additional reason why individuals with schizophrenia use cannabis.
Nevertheless, after the onset of schizophrenia, cannabis use can exacerbate both positive and negative symptoms, and worsen the disease outcome. Even if an individual is stabilized on antipsychotic medication, cannabis use can lead to more frequent relapses and longer hospitalizations. With high potency THC, the risk of these consequences is even greater, as higher doses of THC are associated with worse psychotic symptoms.
In those with schizophrenia, marijuana misuse can lead to:
- Exacerbation of psychotic symptoms: Individuals with schizophrenia who use cannabis experience worse psychotic symptoms than non-users with schizophrenia.14
- Poor treatment compliance: A comorbid diagnosis of cannabis use disorder (CUD) with schizophrenia is associated with poorer medication compliance than a diagnosis of schizophrenia alone.15
- Relapse and re-hospitalizations: Individuals with schizophrenia who have used cannabis tend to have more frequent relapses and longer hospital stays than schizophrenia patients with no history of cannabis use.16
- Depressive symptoms: In one study, schizophrenia patients who continued to misuse cannabis after their first psychotic episode experienced more depressive symptoms five years later than those who discontinued use.17
Can Cannabis Be Used to Treat Schizophrenic Symptoms?
While THC can worsen schizophrenia symptoms, CBD dampens the effects of THC. Marijuana derived from strains of cannabis that have a higher CBD-to-THC ratio is less likely to give as strong a “high,” and it is also less likely to exacerbate schizophrenia symptoms.
When given alone (i.e., without THC), CBD has been shown to reduce inflammation and alleviate psychotic symptoms. In fact, a number of studies have shown CBD to be as effective as some antipsychotic drugs (e.g., amisulpride) and without as many adverse side effects.17,18 Some studies suggest CBD could have a prophylactic role in treating both schizophrenia and drug misuse through the reduction of THC’s effectiveness and the reduction of inflammation.
Limitations & Concerns of CBD in Schizophrenia Treatment
While the use of CBD products has been growing in popularity, it is important to recognize some concerns regarding side effects, interactions, and regulations. Most importantly, be sure to consult with your doctor first.
Some concerns regarding CBD relate to:
- Regulations: In the United States, most CBD products are unregulated. One exception is Epidiolex, which is a purified oral CBD solution to treat epilepsy and approved by the US Food and Drug Administration (FDA). The FDA does not currently recognize other CBD products as drugs or legal dietary supplements.
- Side effects: Though CBD is fairly well-tolerated and may have fewer side effects than antipsychotic drugs, it does have some; and, these may vary depending on the formulation, dose, and interaction with other medications.
- Inaccurate CBD dosage on labels: Many consumers may be unwittingly using a product with an actual dose that is below or above the expected dose. This is further compounded when it is taken multiple times a day and interacts with other medications, or if taken by someone with liver vulnerability.
- Other ingredients: Depending on the product used, other ingredients may be present which may or may not be safe.
Treatment for Schizophrenia
Schizophrenia can be a progressively degenerative condition if left untreated. As with most medical and mental illnesses, the earlier schizophrenia is treated, the better. Given the fear and uncertainty that schizophrenia can instill, an individual who thinks they might be affected would do well to identify a person they most trust, and tell that person what they are experiencing. In turn, that person should consider talking to a physician, mental health provider, or a family member to get treatment recommendations.
A combination of treatment methods is the best way to manage symptoms of schizophrenia. If positive symptoms are present, medication is often a first line of treatment. Therapy, social skills training, and support groups also play an important role in long term treatment and management of the illness.
Medication treatment is often the first and most effective means of alleviating schizophrenia’s most challenging symptoms. However, finding the right medication can be difficult. A skilled psychiatrist can help figure out the best pharmaceutical regimen for you.
Medications used to treat schizophrenia include:
- Typical antipsychotics: Typical antipsychotic medications have numerous serious side effects, but are typically considered a frontline intervention for schizophrenic symptoms.
- Atypical antipsychotics: Second-generation or atypical antipsychotics work differently than typical, modulating both serotonin and dopamine. Clozapine (Clozaril) is the most effective at reducing positive symptoms, but it carries the most dangerous set of side effects.
- Antidepressants/anti-anxiety medications: Other medications commonly used for depression and anxiety may also be used to treat specific negative symptoms of schizophrenia, or to preempt positive symptoms that may be triggered by intense anxiety.
- Injectables: Recently, clinicians have been developing longer-acting antipsychotics that can be injected by medical professionals to avoid reliance on regular daily adherence by the individual with schizophrenia.19
. These injections provide medication for weeks to months with a single shot.
- Cannabidiol (CBD): A number of studies have shown CBD to be as effective as some antipsychotic drugs (e.g., amisulpride) and without as many adverse side effects.18,20
CBD has even shown some potential for use as a preventative in individuals at risk for schizophrenia.
*Please note that most CBD on the market is not regulated and many products have been found to have inaccurate dose information. Furthermore, CBD does have side effects as well and can interact with other medications. It is always recommended to consult with your doctor before using.
A combination of individual therapy along with family therapy is most effective. Individual therapy from a BT or CBT perspective often focuses on concrete goals, like reality testing of one’s hallucinations and delusions, verbal skills enhancement, maintenance of ADLs, and medication compliance. Family therapy often focuses on the ways an individual’s family system can better prevent the afflicted individual from undue anxiety, frustration, or confusion.
If one so chooses, they can take the initiative and take steps to find the right therapist. This may seem daunting, but there are resources that can help, such as an online therapist directory.
Therapeutic options for schizophrenia include:
- Behavior therapy: This therapy module can offer patients concrete rewards for behavior successes, like achieving hygiene goals.
- Cognitive behavioral therapy (CBT): CBT can help individuals learn to perform reality testing on their hallucinations and delusions.
- Family therapy: Family therapy can help family members create an environment of support and positivity that reduces anxiety, anger, and confusion, thus preventing the symptoms before they arise.
- Psychodynamic Therapy: While not typical for schizophrenia, psychodynamic therapy can sometimes be beneficial for patients who have good insight into how their psychotic symptoms may be related to past traumas.
- Social skills training (SST): SST can be particularly useful–especially in conjunction with psychotherapy and medications–to help a person develop skills that are often deficient in schizophrenia.21
Though cannabis has been used for over six millennia, research on how it affects the human body and brain is still in its infancy. As it is increasingly being legalized worldwide, it is imperative that those with schizophrenia understand both potential benefits and risks.