150+ Scientific Studies Showing the Dangers of Marijuana

Marijuana can cause - Brain Damage (Lowered IQ, Memory Loss, Paranoia, Psychosis, Schizophrenia); Mood Disorders (Aggression, Anxiety, Depression, Irritability); Cancer; Heart Attacks; Gum Disease; Impaired Motor Skills; Lung Disease; Obesity; Osteoporosis; Pregnancy Complications; Sexual Dysfunction; Strokes, Viral Infections and even Death.

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Perception of marijuana as a "safe drug" is scientifically inaccurate (Mount Sinai School of Medicine)
Cannabis more damaging to health than previously thought claim doctors (Imperial College London)
NIDA review summarizes research on marijuana’s negative health effects (New England Journal of Medicine)



Brain Damage:
Adolescent Pot Use Leaves Lasting Mental Deficits (Duke University)
Brain-damage risks higher for younger marijuana users, study says (Harvard Medical School)
Cannabis and adolescence: A dangerous cocktail (McGill University Health Centre)
Cannabis 'can cause psychosis in healthy people' (King's College London)
Cannabis Could Increase Risks Of Psychotic Illness By 40 Percent (Cardiff University)
Cannabis increases risk of psychosis (British Medical Journal)
Cannabis increases risk of depression and schizophrenia (British Medical Journal)
Cannabis ingredient causes toxic psychosis (University of Lausanne)
Cannabis link to psychosis (University of New South Wales)
Cannabis smokers 'are taking huge risk of psychotic illness' (King's College London)
Cannabis smoking 'permanently lowers IQ' (Proceedings of the National Academy of Sciences)
Cannabis Triggers Transient Schizophrenia-like Symptoms (Yale School of Medicine)
Cannabis use 'dulls the brain' (Journal of the American Medical Association)
Cannabis use mimics cognitive weakness that can lead to schizophrenia (University of Bergen)
Cannabis use precedes the onset of psychotic symptoms in young people (British Medical Journal)
Casual marijuana use linked to brain abnormalities in students (Northwestern University)
Chronic alcohol and marijuana use during youth can compromise white-matter integrity (University of Pittsburgh Medical Center)
Concerns over mental health risk of smoking cannabis (British Journal of Psychiatry)
Daily Consumption Of Cannabis Predisposes To Appearance Of Psychosis And Schizophrenia (University of Granada)
Daily Pot Smoking May Hasten Onset of Psychosis (Emory University)
Early Cannabis Use Increases Risk of Schizophrenia (University of Otago)
Early cannabis users three times more likely to have psychotic symptoms (University of Queensland)
Frequent Marijuana Use May Affect Brain Function (University of Iowa)
Heavy Cannabis Use May Lead to Psychotic Symptoms (University of Otago)
Heavy Marijuana use has a detrimental impact on intelligence (Canadian Medical Association Journal)
Heavy Marijuana Use May Damage Developing Brain In Teens, Young Adults (Children's Hospital of Philadelphia)
How cannabis causes 'cognitive chaos' in the brain (University of Bristol)
How Marijuana Causes Memory Deficits (Nature Neuroscience)
How marijuana impairs memory (Cell Journal)
How Smoking Marijuana Damages The Fetal Brain (Science)
Human Study Shows Greater Cognitive Deficits in Marijuana Users Who Start Young (Society for Neuroscience)
Imaging Shows Similarities in Brains of Marijuana Smokers, Schizophrenics (Radiological Society of North America)
Imaging Study Shows Awareness Deficit in Marijuana Abusers (Neuropsychopharmacology Journal)
Lab study shows THC exposure as adolescents linked to negative effects of THC as adults (Federation of American Societies for Experimental Biology)
Long-time cannabis use associated with psychosis (Archives of General Psychiatry Journal)
Long-term cannabis use causes brain injury (Archives of General Psychiatry Journal)
Long-term cannabis use may blunt the brain's motivation system (Imperial College London)
Marijuana And Alcohol Taken Together Induced Widespread Nerve Cell Death In Brains Of Young Rats (Annals of Neurology Journal)
Marijuana has damaging effect on brain (King's College London)
Marijuana Use Affects Blood Flow In Brain Even After Abstinence (American Academy of Neurology)
Marijuana use in adolescence may cause permanent brain abnormalities (University of Maryland Medical Center)
Marijuana use in pregnancy damages kids' learning (Proceedings of the National Academy of Sciences)
Marijuana Users Have Abnormal Brain Structure and Poor Memory (Northwestern University)
Memory, speed of thinking get worse over time with marijuana use (American Academy of Neurology)
Mental illness associated with heavy cannabis use (Centre for Addiction and Mental Health)
Molecular Imaging Shows Chronic Marijuana Smoking Affects Brain Chemistry (Society of Nuclear Medicine)
More Evidence Links Early Cannabis Use to Psychosis (City University of New York)
More evidence of cannabis-induced psychosis (BMC Psychiatry Journal)
New RCSI research demonstrates how cannabis use during adolescence affects brain regions associated with schizophrenia (Royal College of Surgeons in Ireland)
New research reveals how cannabis alters brain function (King's College London)
Psychotic illness appears to begin at younger age among those who use cannabis (Archives of General Psychiatry Journal)
Rat study conducted by UGA researchers suggests that cannabis interferes with sustained attention (University of Georgia)
Regular marijuana use bad for teens' brains (American Psychological Association)
Research Finds that Marijuana Use Takes Toll on Adolescent Brain Function (University of Cincinnati)
Scans reveal brain damage from cannabis is like schizophrenia (Albert Einstein College of Medicine)
Schizophrenia Linked To Dysfunction In Molecular Brain Pathway Activated By Marijuana (University of Pittsburgh School of Medicine)
Skunk 'poses greatest risk of psychosis' (King's College London)
Skunk smokers 18 times more likely to be psychotic (Royal College of Psychiatrists)
Smoking cannabis increases the risk of depression in the case of genetic vulnerability (Radboud University)
Starting marijuana use during teens may result in cognitive impairment later in life (National Institute on Drug Abuse)
Study demonstrates link between reclassification of cannabis and cannabis psychosis (University of York)
Study Links Marijuana to Brain Problems (Journal of the American Medical Association)
Teen Drug Use Associated With Psychiatric Disorders Later In Life (National Institute On Drug Abuse)
Teen Marijuana Use Can Lead to Anxiety, Depression, or Aggression (Mount Sinai School of Medicine)
Teen Marijuana Use Worsens Depression: An Analysis of Recent Data Shows 'Self-Medicating' Could Actually Make Things Worse (Office of National Drug Control Policy)

Cancer:
Cannabis alters human DNA -- new study (University of Leicester)
Higher Cancer Risk Found in Marijuana Than in Tobacco (Indiana University)
Marijuana Use Linked to Increased Risk of Testicular Cancer (Fred Hutchinson Cancer Research Center)
Marijuana use may increase risk of testicular cancer (University of Southern California)
New study reveals how cannabis suppresses immune functions: Cannabis compounds found to trigger unique immune cells which promote cancer growth (European Journal of Immunology)
Researchers At UCLA's Jonsson Cancer Center Report Smoking Marijuana May Increase Risk Of Head And Neck Cancers (University of California, Los Angeles)
Sexual Activity and Marijuana Use Associated with HPV-Positive Head and Neck Cancer, Study Shows (Johns Hopkins Kimmel Cancer Center)
Study finds marijuana ingredient promotes tumor growth, impairs anti-tumor defenses (National Institute on Drug Abuse)
Tobacco is 'less risky than dope' (Memorial Sloan–Kettering Cancer Center)

Death:
German study finds cannabis use triggered 2 deaths (Forensic Science International Journal)

Gum Disease:
Heavy Marijuana Use Linked To Gum Disease (Journal of the American Medical Association)

Heart Disease:
Adolescent binging on marijuana linked to stroke (Saint Louis University)
Marijuana use can trigger heart attack (Beth Israel Deaconess Medical Center)
Marijuana use may increase heart complications in young, middle-aged adults (American Heart Association)
Regular Cannabis May Increase Risk Of Stroke In Young Users (British Medical Journal)
Smoking Marijuana Associated With Higher Stroke Risk in Young Adults (American Heart Association)
Study Finds Marijuana Poses Health Threat to Baby Boomers (Beth Israel Deaconess Medical Center)
Study finds possible connection between marijuana abuse and stroke or heart attacks (Molecular Psychiatry Journal)

Lung Disease:
Growing Evidence Of Marijuana Smoke's Potential Dangers (American Chemical Society)
Impact on lungs of 1 cannabis joint equal to up to 5 cigarettes (British Medical Journal)
Long-term Marijuana Smoking Leads To Respiratory Complaints (Yale School of Medicine)
Marijuana associated with same respiratory symptoms as tobacco (Yale School of Medicine)
Marijuana Smoke Contains Higher Levels Of Certain Toxins Than Tobacco Smoke (American Chemical Society)
Marijuana Smokers Face Rapid Lung Destruction -- As Much As 20 Years Ahead Of Tobacco Smokers (Respirology Journal)
Marijuana Smoking Increases Risk Of COPD For Tobacco Smokers (Canadian Medical Association Journal)
Marijuana Worsens COPD Symptoms In Current Cigarette Smokers (American Thoracic Society)
Research Confirms Adverse Effects of Cannabis on Respiratory Health (University of Otago)
Smoking One Joint is Equivalent to 20 Cigarettes (Medical Research Institute of New Zealand)

Obesity:
Binge eating, overeating may be associated with initiating use of marijuana, other drugs (Archives of Pediatrics & Adolescent Medicine Journal)
Machinery Of The 'Marijuana Munchies' (Neuron Journal)

Osteoporosis:
Cannabis use linked to risk of osteoporosis (Nature Medicine)

Pregnancy Complication:
Cannabis during pregnancy endangers fetal brain development (Karolinska Institutet)
Marijuana Use Causes Early Pregnancy Failure (Journal of Clinical Investigation)
Marijuana use could cause tubal pregnancies (Vanderbilt University Medical Center)
Marijuana Use Implicated in Pregnancy Problems (Cincinnati Children’s Hospital Medical Center)
Substance use, social stress compromise pregnant women's immune system (Duke University Medical Center)

Sexual Dysfunction:
Abusing Marijuana May Overload System, Inhibit Fertility (University at Buffalo)
Marijuana-Like Compounds May Alter Human Fertility (University at Buffalo)
Researcher connects cannabis use and sexual dysfunction (Queen's University)
Sperm From Marijuana Smokers Move Too Fast Too Early, Impairing Fertility (University at Buffalo)
Sperm size and shape in young men affected by cannabis use (University of Sheffield)

Sleep Disorder:
Marijuana use is associated with impaired sleep quality (American Academy of Sleep Medicine)

Viral Infection:
Marijuana Component Opens The Door For Virus That Causes Kaposi's Sarcoma (American Association for Cancer Research)
Regular Marijuana Use Increases Risk Of Hepatitis C-related Liver Damage (American Gastroenterological Association)

Vehicle Accidents:
Cannabis almost doubles risk of fatal crashes (British Medical Journal)
Cannabis use doubles chances of vehicle crash (British Medical Journal)
Driving under influence of cannabis more common and riskier than drink driving (University of Otago)
Marijuana use involved in more fatal accidents in Colorado (University of Colorado School of Medicine)
Marijuana use may double the risk of accidents for drivers (Columbia University)
Signs point to sharp rise in drugged driving fatalities (Columbia University)
Study finds cannabis use, dangerous driving behaviors interrelated (University of Montreal)
Teens who use alcohol and marijuana together are at higher risk for unsafe driving (Journal of Studies on Alcohol and Drugs)
The dangers of taking the "high" road: Increased collision risk, skill impairment (Dalhousie University)

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Addiction:
Animals Exposed To Marijuana's Active Component Will Self-Administer The Drug (National Institute on Drug Abuse)
Cannabis withdrawal symptoms might have clinical importance (Public Library of Science Journal)
Chronic Marijuana Users Become Aggressive During Withdrawal (Harvard Medical School)
Increase in prevalence of marijuana abuse and dependence (Journal of the American Medical Association)
Marijuana dependence alters the brain's response to drug paraphernalia (University of Texas at Dallas)
Marijuana Withdrawal As Bad As Withdrawal From Cigarettes (Johns Hopkins University School of Medicine)
Marijuana Withdrawal Reported By Teens Seeking Treatment (University of Vermont)
Mothers' Teen Cannabinoid Exposure May Increase Response of Offspring to Opiate Drugs (Tufts University)
Parental exposure to THC Linked to drug addiction, compulsive behavior in unexposed offspring (Mount Sinai Medical Center)
Regular cocaine and cannabis use may trigger addictive behaviours (British Journal of Pharmacology)
Smoking, Drinking, Drugs: The Younger They Start, The Harder It Is To Quit (Center for Advancing Health)
Troubled Teens Risk Rapid Dependence on Marijuana (University of Colorado School of Medicine)

Gateway Drug:
A 'yes' to one drug could become ‘yes’ for other drugs (Prevention Science Journal)
Cannabis linked to use of amphetamines (Addiction Journal)
Brain Studies Tie Marijuana to Other Drugs (Science)
Early marijuana use increases risk of drug and alcohol problems later in life (Washington University School of Medicine)
Illicit Drug Use Starts With Cannabis (University of Otago)
Marijuana use linked to hallucinogen use (Johns Hopkins University Bloomberg School of Public Health)
National Study Shows "Gateway" Drugs Lead to Cocaine Use (Columbia University)
Study suggests cannabis-users may be vulnerable to harder drugs (Mount Sinai School of Medicine)

Legalization:
Decriminalizing pot may land more kids in the ER (American College of Emergency Physicians)
High School Seniors’ Marijuana Use Expected to Increase with Legalization (New York University)
Increase in unintentional marijuana ingestion among children following new drug laws in Colorado (Journal of the American Medical Association Pediatrics)
Legalizing marijuana in California would lower the price of the drug and increase use (RAND Corporation)
Legalizing marijuana in California would not substantially cut cartel revenues (RAND Corporation)

Sociological:
African-American Girls Who Use Marijuana Engage In Riskier Sex, Have Higher STD Rate (Emory University)
Children who smoke cannabis are twice as likely to offend (Queen's University Belfast)
Early Exposure To Drugs, Alcohol Creates Lifetime Of Health Risk (Psychological Science Journal)
Father's incarceration associated with elevated risks of marijuana and other illegal drug use (Bowling Green State University)
First-Year College Students Show High Rate of Cannabis Use Disorders (University of Maryland, College Park)
Future generations could inherit drug and alcohol use (Sam Houston State University)
Malt Liquor Linked To Marijuana Use Among Young Adults (University at Buffalo)
New study finds glamorization of drugs in rap music jumped dramatically over two decades (University of California, Berkeley)
One Of Every Three Popular Songs Contains References To Substance Use (American Public Health Association)
Pot and pop: New research finds stronger link between music and marijuana use among teens (University of Pittsburgh Schools of the Health Sciences)
References To Explicit Substance Use Common In Popular Music (Archives of Pediatrics & Adolescent Medicine Journal)
Researchers Find Factors That Encourage Cannabis Use Among University Students (Journal of Applied Biobehavioral Research)
Rising Teen Marijuana Use Is Fueled By Change In Attitudes (American Journal of Public Health)
Teens who frequently go out with friends more likely to use marijuana (Archives of Pediatrics & Adolescent Medicine Journal)

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Medical Marijuana Myth - Alzheimer Treatment:
Marijuana ineffective as an Alzheimer’s treatment (University of British Columbia)

Medical Marijuana Myth - Multiple Sclerosis (MS) Treatment:
Active ingredient of cannabis has no effect on the progression of multiple sclerosis (Peninsula College of Medicine and Dentistry)
Added benefit of Cannabis sativa for spasticity due to multiple sclerosis is not proven (Institute for Quality and Efficiency in Health Care)
Cannabis constituent has no effect on MS progression (Plymouth University)
Jury's Still Out on Use of Marijuana Derivative for MS (American Academy of Neurology)
Marijuana Use May Hurt Intellectual Skills in MS Patients (American Academy of Neurology)
No strong evidence to back use of cannabis extract in Multiple Sclerosis (British Medical Journal)
Smoking Marijuana Impairs Cognitive Function in MS Patients (American Academy of Neurology)

Medical Marijuana Myth - Nausea Relief:
Marijuana use associated with cyclic vomiting syndrome in young males (Neurogastroenterology and Motility Journal)
Marijuana use may cause severe cyclic nausea, vomiting, a little-known, but costly effect (American College of Gastroenterology)
Severe Vomiting Sickness With Chronic Cannabis Abuse (World Journal of Gastroenterology)

Medical Marijuana Myth - Pain Relief:
Active ingredients in marijuana found to spread and prolong pain (University of Texas Medical Branch at Galveston)
Cannabis 'no better than codeine' for headaches (British Medical Journal)
Doubts on cannabis for pain relief (Flinders Medical Centre)
Endocannabinoids can promote pain (ETH Zurich)
Medical Marijuana Not the Answer for Teens with Chronic Pain, Mayo Clinic Doctors Say (Mayo Clinic)
Oral Cannabis Ineffective In Treating Acute Pain (Journal of Anesthesiology)
Too Much Marijuana Makes Pain Worse, Not Better (University of California, San Diego)

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Sources: (128)

Addiction Journal
Albert Einstein College of Medicine
American Academy of Neurology
American Academy of Sleep Medicine
American Association for Cancer Research
American Chemical Society
American College of Emergency Physicians
American College of Gastroenterology
American Gastroenterological Association
American Heart Association
American Journal of Public Health
American Psychological Association
American Public Health Association
American Thoracic Society
Annals of Neurology Journal
Archives of General Psychiatry Journal
Archives of Pediatrics & Adolescent Medicine Journal
Autonomous University of Barcelona
Beth Israel Deaconess Medical Center
BMC Psychiatry Journal
Bowling Green State University
British Journal of Pharmacology
British Journal of Psychiatry
British Medical Journal
Canadian Medical Association Journal
Cardiff University
Cell Journal
Center for Advancing Health
Centre for Addiction and Mental Health
Children's Hospital of Philadelphia
Cincinnati Children’s Hospital Medical Center
City University of New York
Columbia University
Dalhousie University
Duke University
Duke University Medical Center
Emory University
ETH Zurich
European Journal of Immunology
Federation of American Societies for Experimental Biology
Flinders Medical Centre
Forensic Science International Journal
Fred Hutchinson Cancer Research Center
Harvard Medical School
Imperial College London
Indiana University
Institute for Quality and Efficiency in Health Care
Johns Hopkins Kimmel Cancer Center
Johns Hopkins University Bloomberg School of Public Health
Johns Hopkins University School of Medicine
Journal of Anesthesiology
Journal of Applied Biobehavioral Research
Journal of Clinical Investigation
Journal of Studies on Alcohol and Drugs
Journal of the American Medical Association
Journal of the American Medical Association Pediatrics
Karolinska Institutet
King's College London
Mayo Clinic
McGill University Health Centre
Medical Research Institute of New Zealand
Memorial Sloan–Kettering Cancer Center
Molecular Psychiatry Journal
Mount Sinai Medical Center
Mount Sinai School of Medicine
National Institute on Drug Abuse
Nature Medicine
Nature Neuroscience
Neurogastroenterology and Motility Journal
Neuron Journal
Neuropsychopharmacology Journal
New England Journal of Medicine
New York University
Northwestern University
Office of National Drug Control Policy
Peninsula College of Medicine and Dentistry
Plymouth University
Prevention Science Journal
Proceedings of the National Academy of Sciences
Psychological Science Journal
Public Library of Science Journal
Queen's University
Queen's University Belfast
Radboud University
Radiological Society of North America
RAND Corporation
Respirology Journal
Royal College of Psychiatrists
Royal College of Surgeons in Ireland
Saint Louis University
Sam Houston State University
Science
Society for Neuroscience
Society of Nuclear Medicine
Tufts University
University at Buffalo
University of Bergen
University of Bristol
University of British Columbia
University of California, Berkeley
University of California, Los Angeles
University of California, San Diego
University of Cincinnati
University of Colorado School of Medicine
University of Granada
University of Georgia
University of Iowa
University of Lausanne
University of Leicester
University of Maryland, College Park
University of Maryland Medical Center
University of Montreal
University of New South Wales
University of Otago
University of Pittsburgh Medical Center
University of Pittsburgh School of Medicine
University of Pittsburgh Schools of the Health Sciences
University of Queensland
University of Sheffield
University of Southern California
University of Texas at Dallas
University of Texas Medical Branch at Galveston
University of Vermont
University of York
Vanderbilt University Medical Center
Washington University School of Medicine
World Journal of Gastroenterology
Yale School of Medicine

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