Marijuana and Mental Health: What Today’s Cannabis Can Do to the Brain

Marijuana has changed substantially over the past several decades.

What many people remember as marijuana from the late 1960s or 1970s is not necessarily comparable to many cannabis products being smoked, vaped, eaten, or concentrated today. Modern products may contain substantially higher concentrations of tetrahydrocannabinol (THC), the primary cannabinoid responsible for marijuana's intoxicating effects.

For some people, cannabis produces relaxation or euphoria. For others—particularly with higher doses or high-potency THC—the experience can involve panic, paranoia, hallucinations, disorganized thinking, or even psychosis.

Recent research has raised particular concerns about high-potency THC, cannabis-use disorder, adolescent exposure, and psychotic symptoms. A 2025 systematic review published in Annals of Internal Medicine reviewed 99 studies involving more than 221,000 participants and found particularly consistent unfavorable associations between high-concentration THC products and psychosis/schizophrenia and cannabis-use disorder.

What Is Marijuana?

Marijuana, more accurately called cannabis, comes primarily from plants belonging to the Cannabis genus.

The cannabis plant contains numerous biologically active compounds known as cannabinoids.

The two best known are:

THC — Delta-9-tetrahydrocannabinol

THC is the cannabinoid primarily responsible for intoxication and the marijuana "high."

CBD — Cannabidiol

CBD generally does not produce the intoxicating effects associated with THC and has a substantially different pharmacological profile.

Cannabis products can now be consumed in many forms, including:

• Smoked marijuana flower
• Vaping products
• Edibles
• Gummies
• Beverages
• Oils
• Tinctures
• Wax
• Shatter
• "Dabs"
• Other concentrated THC preparations

The amount of THC delivered by these products can vary tremendously.

What Does a Marijuana High Feel Like?

The subjective effects of cannabis vary considerably.

Effects depend upon:

• THC concentration
• Amount consumed
• Route of administration
• Previous cannabis exposure
• Individual genetics
• Age
• Psychiatric history
• Other medications or substances
• CBD concentration

A typical cannabis high may involve:

• Relaxation
• Euphoria
• Increased laughter
• Changes in sensory perception
• Altered perception of time
• Increased appetite
• Drowsiness
• Increased awareness of music, colors, or surroundings

But THC does not always produce a pleasant experience.

Higher doses can cause:

• Anxiety
• Panic
• Racing thoughts
• Rapid heart rate
• Confusion
• Depersonalization
• Derealization
• Suspiciousness
• Paranoia
• Hallucinations
• Delusional thinking
• Severe agitation

In some people, cannabis exposure can precipitate a clinically significant cannabis-induced psychotic episode.

Marijuana Today Is Not the Marijuana of the 1960s and 1970s

One of the most important changes in cannabis is the increase in THC potency.

Historical analyses of cannabis seized in the United States have demonstrated a major increase in THC concentrations over several decades.

Modern cannabis flower commonly contains THC concentrations that would have been unusual decades ago, and cannabis concentrates may contain dramatically higher THC levels still.

This matters clinically because the psychiatric effects of cannabis appear to depend partly upon the amount and concentration of THC a person receives.

A major 2025 systematic review of high-concentration THC products evaluated 99 studies involving 221,097 participants. Among non-therapeutic studies, unfavorable associations were particularly consistent for psychosis or schizophrenia and cannabis-use disorder.

Therefore, smoking marijuana in 2026 cannot automatically be considered equivalent to smoking marijuana in 1970.

The drug may carry the same name, but the THC exposure can be dramatically different.

Sativa vs. Indica: What Is the Difference?

Cannabis products are commonly categorized as:

Sativa

Traditionally marketed as:

• Energizing
• Uplifting
• Creative
• Cerebral
• Stimulating

Indica

Traditionally marketed as:

• Relaxing
• Sedating
• Calming
• Sleep-promoting
• More physically oriented

Hybrid

Supposedly containing characteristics of both.

However, these labels should not be treated as reliable medical predictors of how someone will respond.

Modern cannabis plants have undergone extensive hybridization. The actual psychoactive response is more strongly influenced by factors such as:

THC concentration + CBD concentration + other cannabinoids + terpenes + dose + individual biology

rather than the simple Sativa or Indica label.

For psychiatric purposes, THC potency is considerably more important than whether a dispensary labels a product "Sativa" or "Indica."

Which Marijuana Strain Is Most Likely to Cause Paranoia or Psychosis?

There is no scientifically established individual marijuana strain that can reliably be identified as "the psychosis strain."

The larger concern is high-potency THC, particularly when THC levels are high and CBD exposure is relatively low.

A 2024 longitudinal cohort study published in Addiction followed young people into adulthood. Those reporting high-potency cannabis use during adolescence had approximately twice the likelihood of developing new psychotic experiences between ages 19 and 24 compared with the reference group.

Another 2024 study examining cannabis potency and adolescent mental health found that adolescents reporting high-potency cannabis use were more likely to report symptoms of depression and showed concerning associations with anxiety and auditory hallucinations.

Therefore:

High THC matters more clinically than whether the cannabis is called Sativa or Indica.

A high-THC Indica could potentially present substantially more psychiatric risk than a low-THC Sativa, and vice versa.

What Does Marijuana Do in the Brain?

The human nervous system contains an endocannabinoid system.

This signaling system participates in the regulation of:

• Mood
• Memory
• Learning
• Reward
• Stress
• Appetite
• Sleep
• Pain
• Motivation
• Motor coordination

THC partially mimics naturally occurring cannabinoid signaling molecules and primarily acts on CB1 cannabinoid receptors within the central nervous system.

CB1 receptors are found throughout multiple brain regions.

Hippocampus

Important for memory and learning.

THC can interfere with short-term memory formation and information processing.

Prefrontal Cortex

Important for:

• Judgment
• Planning
• Attention
• Decision-making
• Impulse control

THC can temporarily impair these higher-order cognitive functions.

Amygdala

The amygdala plays a major role in fear and threat perception.

In vulnerable individuals, disruption of these networks may contribute to:

• Anxiety
• Fear
• Suspiciousness
• Paranoia

Basal Ganglia

These regions participate in movement, habits, motivation, and reward.

Cerebellum

The cerebellum contributes to coordination, balance, timing, and motor control.

Reward and Dopamine Systems

THC also indirectly influences dopamine signaling.

These reward circuits contribute to:

• Reinforcement
• Motivation
• Craving
• Development of cannabis-use disorder

THC also alters the balance of neurotransmitter systems such as GABA and glutamate, helping explain why high doses may dramatically alter perception, memory, cognition, anxiety, and thought organization.

Does Marijuana Cause Brain Damage?

This question requires careful wording.

It would be scientifically inaccurate to claim that every individual who uses cannabis develops permanent "brain damage."

Research does, however, show associations between heavy or frequent cannabis exposure—particularly beginning during adolescence—and differences involving:

• Memory
• Attention
• Executive function
• Brain activation
• Neural connectivity
• Cognitive performance

The important distinction is between demonstrating an association and proving that cannabis directly caused every observed brain difference.

Cannabis users may differ from non-users in many ways, and researchers attempt to control for these factors.

Nevertheless, adolescence is considered a particularly important period because the brain is still undergoing substantial development.

The greater concerns generally involve:

• Younger age at initiation
• Frequent consumption
• Heavy consumption
• High-potency THC
• Long duration of use

Can Marijuana Cause Mental-Health Problems?

Yes.

Cannabis does not affect everyone in the same way, but it can trigger or worsen psychiatric symptoms.

Possible effects include:

• Anxiety
• Panic attacks
• Paranoia
• Cognitive impairment
• Depersonalization
• Derealization
• Sleep disturbance
• Depression in some individuals
• Cannabis-use disorder
• Withdrawal symptoms
• Hallucinations
• Psychotic symptoms

Higher-potency cannabis appears particularly concerning.

The 2025 Annals of Internal Medicine systematic review found that high-concentration THC products showed particularly consistent unfavorable associations with psychosis/schizophrenia and cannabis-use disorder.

Can Marijuana Cause Psychosis?

Yes.

Cannabis can precipitate a condition clinicians recognize as cannabis-induced psychotic disorder.

Symptoms can include:

• Severe paranoia
• Delusions
• Auditory hallucinations
• Visual hallucinations
• Disorganized thinking
• Disorganized speech
• Suspiciousness
• Intense fear
• Agitation
• Loss of touch with reality

Psychotic symptoms may sometimes resolve following cessation of cannabis.

However, symptoms can occasionally continue well beyond the immediate period of intoxication.

Anyone experiencing persistent hallucinations, delusions, severe paranoia, dangerous behavior, or inability to distinguish reality from distorted perceptions warrants urgent psychiatric assessment.

Can Marijuana Cause Schizophrenia?

This question also requires nuance.

Using marijuana does not mean someone will automatically develop schizophrenia.

Many people use cannabis and never develop a psychotic disorder.

However, cannabis exposure is associated with an increased risk of psychotic outcomes, particularly when use involves:

• High-potency THC
• Frequent cannabis use
• Early initiation
• Heavy exposure
• Existing vulnerability to psychosis

The 2024 longitudinal study by Hines and colleagues found that adolescent high-potency cannabis exposure was associated with an approximately 2.15-fold higher likelihood of new psychotic experiences between ages 19 and 24.

The much larger 2025 systematic review of high-concentration THC products likewise concluded that high-concentration THC was associated with unfavorable mental-health outcomes, particularly psychosis/schizophrenia and cannabis-use disorder.

Scientists continue studying exactly how cannabis interacts with genetics and other vulnerabilities.

One possible interpretation is that high-THC cannabis may act as a precipitating factor in individuals who already possess biological vulnerability to psychosis.

People with:

• Schizophrenia
• Previous psychosis
• Previous cannabis-induced psychosis
• Bipolar disorder with psychotic symptoms
• Strong family histories of psychotic disorders

should therefore discuss cannabis exposure carefully with their psychiatric clinician.

What About Synthetic Marijuana—Spice and K2?

Spice and K2 are not simply stronger forms of marijuana.

They usually contain laboratory-created chemicals known as synthetic cannabinoid receptor agonists.

These chemicals can stimulate cannabinoid receptors very differently—and sometimes much more powerfully—than naturally occurring THC.

A systematic review of K2/Spice toxicity found reports of significant neurological, cardiovascular, and psychiatric toxicity associated with synthetic cannabinoids, including seizures and neuropsychiatric complications. The review concluded that synthetic cannabinoids may exhibit greater toxicity than THC.

Potential effects can include:

• Extreme paranoia
• Psychosis
• Hallucinations
• Seizures
• Loss of consciousness
• Rapid heart rate
• Hypertension
• Severe agitation
• Rhabdomyolysis
• Dangerous behavioral disturbances

These products are particularly concerning because someone may not know exactly which chemical they have consumed.

Can Marijuana Purchased on the Street Contain Other Drugs?

Yes, illicit cannabis carries an additional problem:

You cannot necessarily verify what is actually in the product.

Unregulated marijuana may potentially contain:

• Synthetic cannabinoids
• Pesticides
• Mold
• Heavy metals
• Solvents
• Unexpected cannabinoids
• Other contaminants

However, one important misconception deserves clarification.

What About Fentanyl-Laced Marijuana?

There have been highly publicized claims of marijuana being contaminated with fentanyl.

Clinically, this should not be described as a common or widespread phenomenon because current evidence does not support that conclusion.

There have been isolated reports of suspected or confirmed contamination, but widespread intentional fentanyl adulteration of marijuana has not been demonstrated.

That distinction is important.

Patients should still recognize that unregulated street drugs inherently carry greater uncertainty, but unnecessarily exaggerating fentanyl contamination can weaken otherwise legitimate harm-reduction messages.

Synthetic cannabinoids such as Spice/K2 represent a much better documented cannabis-related adulteration and toxicity concern.

Where Is Recreational Marijuana Legal?

Cannabis law remains complicated because federal and state laws differ.

According to the National Conference of State Legislatures' September 2026 cannabis law update, 24 states, three U.S. territories, and the District of Columbia allow or regulate non-medical adult cannabis use.

The 24 states are:

• Alaska
• Arizona
• California
• Colorado
• Connecticut
• Delaware
• Illinois
• Maine
• Maryland
• Massachusetts
• Michigan
• Minnesota
• Missouri
• Montana
• Nevada
• New Jersey
• New Mexico
• New York
• Ohio
• Oregon
• Rhode Island
• Vermont
• Virginia
• Washington

Washington, D.C. also permits adult possession and use under district law, although its commercial framework differs from those of many states.

Cannabis laws continue to evolve, so patients should verify current state regulations before relying on any nationwide list.

Where Is Medical Marijuana Legal?

According to the National Conference of State Legislatures, 41 states, three territories, and Washington, D.C. permit comprehensive medical cannabis programs.

An additional seven states allow limited low-THC/high-CBD products for specific medical circumstances but are not considered comprehensive medical cannabis programs by NCSL.

What Diagnoses Qualify for a Medical Marijuana Card?

There is no universal national list.

Each state determines which illnesses qualify for its medical cannabis program.

Common qualifying diagnoses or symptoms across various states may include:

• Cancer
• Chronic or severe pain
• Epilepsy
• Seizure disorders
• Multiple sclerosis
• Severe muscle spasticity
• HIV/AIDS
• Crohn's disease
• Neuropathic pain
• Parkinson's disease
• Amyotrophic lateral sclerosis
• Severe nausea
• Cachexia or wasting syndrome
• PTSD
• Terminal illnesses

Qualification under state law also does not automatically mean that cannabis is medically appropriate for every individual with that diagnosis.

What Qualifies in Mississippi?

Because Turned Leaf Psychiatry serves Mississippi patients, the state's requirements are particularly relevant.

According to the Mississippi Medical Cannabis Program, qualifying conditions currently include:

• Cancer
• Parkinson's disease
• Huntington's disease
• Muscular dystrophy
• Glaucoma
• Spastic quadriplegia
• HIV
• AIDS
• Hepatitis
• ALS
• Crohn's disease
• Ulcerative colitis
• Sickle-cell anemia
• Alzheimer's disease
• Agitation associated with dementia
• PTSD
• Autism
• Pain refractory to appropriate opioid management
• Diabetic/peripheral neuropathy
• Spinal-cord disease or severe spinal-cord injury

The state also permits certain chronic terminal or debilitating conditions producing:

• Cachexia/wasting syndrome
• Chronic pain
• Severe or intractable nausea
• Seizures
• Severe and persistent muscle spasms

The Mississippi Medical Cannabis Program's patient FAQ provides additional information regarding qualification and patient registration.

Would We Recommend Marijuana for Someone With Mental Illness?

There is no responsible universal answer.

Cannabis does have recognized medical applications in certain circumstances.

However, from a psychiatric standpoint, high-THC cannabis deserves significant caution.

That caution becomes especially important for individuals with:

• Previous psychosis
• Schizophrenia
• Severe paranoia
• Previous cannabis-induced psychosis
• Cannabis-use disorder
• Bipolar disorder involving psychotic symptoms
• Strong family histories of schizophrenia or psychosis

The issue is particularly important because modern high-THC products may produce exposure considerably greater than traditional cannabis.

The 2025 systematic review of high-concentration THC products found the most consistently unfavorable associations with psychosis/schizophrenia and cannabis-use disorder.

Therefore, psychiatric history should be taken into consideration before a person begins or continues high-THC cannabis use.

What Is Cannabis Use Disorder?

Cannabis can become addictive.

Cannabis Use Disorder (CUD) develops when cannabis use becomes increasingly difficult to control and begins producing clinically significant impairment or distress.

Warning signs can include:

• Using more cannabis than intended
• Repeated unsuccessful attempts to reduce use
• Strong cravings
• Spending considerable time obtaining or using cannabis
• Continuing despite psychiatric problems
• Increasing tolerance
• Withdrawal symptoms
• Neglecting work, school, or family responsibilities
• Giving up important activities
• Continuing despite interpersonal consequences

Cannabis withdrawal may include:

• Irritability
• Anxiety
• Insomnia
• Vivid dreams
• Reduced appetite
• Restlessness
• Depressed mood
• Cravings

How Is Cannabis Addiction Treated?

There is currently no universally established FDA-approved medication specifically for cannabis-use disorder.

Behavioral treatments therefore remain particularly important.

A 2025 systematic review and meta-analysis of 22 randomized controlled trials involving 3,304 participants found that motivational enhancement therapy combined with cognitive behavioral therapy (MET-CBT) improved abstinence outcomes compared with inactive or nonspecific controls.

The same review found promising evidence for other psychological approaches, although researchers rated much of the overall evidence as low or very low certainty.

Treatment may include:

• Cognitive Behavioral Therapy
• Motivational Enhancement Therapy
• Motivational Interviewing
• Contingency Management
• Acceptance and Commitment Therapy
• Relapse-prevention strategies
• Substance-use counseling
• Family involvement when appropriate
• Treatment of co-occurring psychiatric illnesses

Treatment should also examine why the individual is using cannabis.

Someone may be attempting to self-medicate:

• Anxiety
• Depression
• Trauma
• ADHD
• Insomnia
• Chronic pain
• Bipolar symptoms

Treating the underlying disorder can be an essential part of successful cannabis recovery.

What Medications Are Used for Cannabis Addiction?

Researchers have investigated multiple medications for cannabis-use disorder and withdrawal.

However, there is currently no single medication considered the established FDA-approved treatment for cannabis-use disorder.

Treatment therefore focuses largely on evidence-based behavioral interventions while clinicians appropriately manage:

• Insomnia
• Anxiety
• Depression
• Mood instability
• ADHD
• PTSD
• Other co-occurring psychiatric conditions

Medication selection must be individualized rather than attempting to treat every person with cannabis-use disorder using the same medication.

How Is Cannabis-Induced Psychosis Treated?

The most important initial step is typically:

Stop further THC exposure.

Someone experiencing severe hallucinations, paranoia, agitation, suicidal thoughts, violent behavior, profound confusion, or inability to care for themselves may require immediate emergency psychiatric or medical evaluation.

Treatment depends upon severity but may include:

• A calm, low-stimulation environment
• Hydration
• Medical monitoring
• Treatment of severe agitation
• Treatment of severe anxiety
• Antipsychotic medication when clinically indicated
• Continued cannabis abstinence
• Substance-use treatment
• Psychiatric follow-up

Antipsychotic medications may sometimes be required when substantial psychotic symptoms persist.

Examples of medications clinicians may consider depending upon the individual presentation include:

• Risperidone
• Olanzapine
• Aripiprazole
• Other antipsychotic medications

The medication choice depends upon the patient's symptoms, medical history, age, metabolic risk, previous responses, and severity of illness.

Long-term follow-up is also important because clinicians need to determine whether symptoms:

• completely disappear following cannabis abstinence, or
• represent the beginning or worsening of an underlying primary psychotic disorder.

Recent Research on Marijuana and Mental Health

Here are several recent studies particularly relevant to patients and psychiatric clinicians:

1. High-Concentration THC and Mental Health — 2025

The 2025 Annals of Internal Medicine systematic review examined 99 studies and 221,097 participants.

Researchers found particularly consistent unfavorable associations between high-concentration THC products and:

• Psychosis/schizophrenia
• Cannabis-use disorder

The researchers also cautioned that many of the included studies had moderate or high risk of bias.

2. High-Potency Cannabis and Later Psychotic Experiences — 2024

A 2024 longitudinal cohort study in Addiction evaluated cannabis exposure during adolescence and later psychotic experiences.

High-potency cannabis use at ages 16 or 18 was associated with approximately 2.15 times the likelihood of new psychotic experiences between ages 19 and 24.

3. Cannabis Potency and Adolescent Mental Health — 2024

A 2024 study examining cannabis potency among adolescents found associations between high-potency cannabis and increased symptoms of probable depression, with concerning findings involving anxiety and auditory hallucinations as well.

4. High-Potency Cannabis, Mental-Health Symptoms, and Dependence

A study examining objectively measured cannabis potency compared cannabis potency with psychiatric symptoms and dependence. Researchers analyzed actual cannabis samples in addition to participants' self-reported potency preferences, providing another approach for investigating how THC concentration relates to mental-health outcomes.

5. Cannabis-Use-Disorder Psychotherapy — 2025

A 2025 systematic review and meta-analysis examined 22 randomized clinical trials containing 3,304 participants.

Motivational enhancement combined with CBT increased abstinence outcomes compared with inactive or nonspecific treatment, although the authors cautioned that confidence in several treatment estimates remained limited.

6. Synthetic Cannabinoid Toxicity

A systematic review examining K2/Spice toxicity documented significant neurological, cardiovascular, and psychiatric complications from synthetic cannabinoids and concluded these compounds may be more toxic than THC.

When Marijuana Stops Feeling Relaxing

One misconception surrounding marijuana is that because cannabis is a plant, it must be harmless.

The brain does not distinguish between a substance being "natural" and a substance being pharmacologically active.

THC interacts directly with an important neurological signaling system.

For one person cannabis may produce relaxation. For another it may produce panic, paranoia, dissociation, addiction, hallucinations, or psychosis.

The risk deserves particular attention with:

• High-potency THC
• Heavy use
• Frequent use
• Younger age of initiation
• Previous psychiatric illness
• Previous psychosis
• Family vulnerability to psychotic disorders

If marijuana once made you feel relaxed but now makes you anxious, suspicious, detached, paranoid, depressed, or "not yourself," the change is worth taking seriously.

How Turned Leaf Psychiatry Can Help

If cannabis appears to be affecting your mood, anxiety, thinking, sleep, concentration, relationships, or ability to function, Turned Leaf Psychiatry can help determine what may actually be occurring.

A comprehensive psychiatric evaluation can help distinguish among:

• Cannabis intoxication
• Cannabis withdrawal
• Cannabis-use disorder
• Cannabis-induced anxiety
• Cannabis-induced psychosis
• Panic disorder
• Bipolar disorder
• Major depressive disorder
• ADHD
• PTSD
• Schizophrenia-spectrum disorders
• Other psychiatric conditions that cannabis may be worsening or masking

Treatment can then be individualized and may involve:

• Comprehensive psychiatric evaluation
• Medication management when clinically appropriate
• Cognitive Behavioral Therapy strategies
• Motivational Interviewing
• Substance-use treatment
• Relapse-prevention planning
• Treatment of underlying psychiatric conditions
• Continued psychiatric monitoring

Someone who develops cannabis-associated psychosis deserves particularly careful follow-up.

The goal is not simply to make the immediate symptoms disappear.

The goal is also to determine:

• Why did this happen?
• Is an underlying psychiatric illness present?
• How can another episode be prevented?

When to Seek Emergency Help

Cannabis-related psychiatric symptoms can occasionally constitute an emergency.

Seek immediate medical assistance for:

• Severe hallucinations
• Extreme paranoia
• Suicidal thoughts
• Homicidal thoughts
• Violent or uncontrollable behavior
• Severe confusion
• Seizures
• Loss of consciousness
• Chest pain
• Severe agitation
• Inability to distinguish reality from hallucinations or delusions

Schedule an Evaluation With Turned Leaf Psychiatry

If marijuana is affecting your anxiety, mood, thinking, motivation, sleep, or ability to function, our Ridgeland, Mississippi team can provide a comprehensive psychiatric evaluation and individualized treatment plan.

Request an appointment → or call (601) 494-5503.

Innovative | Personalized | Evidence-Based

If you are having thoughts of harming yourself or someone else, call or text 988 or call 911 right away.

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Medical disclaimer: This article is provided for educational purposes only and does not constitute individualized medical advice, diagnosis, or treatment. Cannabis risks vary considerably according to potency, dose, frequency, age, psychiatric history, medical history, medications, and other substances being used. A healthcare professional should evaluate individual treatment decisions. Severe psychosis, suicidal thoughts, seizures, extreme agitation, chest pain, or other acute symptoms warrant immediate emergency evaluation.