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  • Writer's pictureBreathe Free Oregon

Dangerous or negative effects of CBD and marijuana

Updated: Oct 3, 2022

This extensive article discusses, among other things, a number of dangerous and negative effects of CBD and marijuana on health, including heart, lungs, mental health, motor coordination for driving, cognitive function, brain development for children, adverse effects on fetuses, addiction, and more.


The short-term effects of marijuana or cannabinoid use include:

  • increased heart rate

  • low blood pressure, orthostatic hypotension muscle relaxation

  • slowed digestion

  • dizziness

  • distorted perception (sights, sounds, time, touch)

  • difficulty in thinking, memory, and problem solving

  • loss of coordination and motor skills

  • agitation, anxiety, confusion, panic, paranoia

  • increased appetite

  • dry mouth, dry eyes

"Reaction time may be impaired while driving. NIDA research shows that drivers have slower reaction times, impaired judgment, and problems responding to signals and sounds if driving while under the influence of THC."

Withdrawal effects:

  • anxiety

  • agitation

  • tremulousness

  • elevation of vital signs

  • insomnia

  • irritability

Mental health effects:

"Marijuana also may affect mental health. Studies show that use may increase the risk of developing psychosis (a severe mental disorder in which there is a loss of contact with reality) including false ideas about what is happening (delusions) and seeing or hearing things that aren’t there (hallucinations), particularly if you carry a genetic vulnerability to the disease."

"Panic attacks, paranoia and psychosis may occur acutely..."

Effects on the heart:

"One study from Mittleman, et al has suggested that the risk of heart attack may increase by up to 4.8-fold in the first hour after smoking marijuana."

"Harvard Health also reports that the risk of a heart attack is several times higher in the hour after smoking marijuana than it would be normally..."

"The risk of stroke may be increased, as well."

Effects on the lungs:

"Marijuana smoke contains many of the same cancer-causing chemicals found in cigarette smoke, often in greater quantities, as reported by Mehmedic and colleagues. Both types of smoke contain cancer-causing nitrosamines, polycyclic aromatic hydrocarbons, vinyl chlorides, and phenol per research reported by Martinasek. Studies have shown that marijuana smoke contains 50 to 70 percent more carcinogenic hydrocarbons than tobacco smoke, and is an irritant to the lungs."

"A 2016 systematic review of the respiratory effects of inhalational marijuana from Martinasek, et al indicates that there is a risk of lung cancer from inhalational marijuana as well as an association between inhalational marijuana and spontaneous pneumothorax, emphysema, or COPD. In the review, eight of the 12 studies indicated an increased risk of lung cancer from cannabis use or cases indicating lung cancer occurrence."

Pregnancy and breastfeeding:

"Marijuana is also the most common illicit drug used during pregnancy, in roughly 2% to 5% of women."

"According to a 2017 updated report published by the American College of Obstetricians and Gynecologists (ACOG) entitled Marijuana Use During Pregnancy and Lactation, 34% to 60% of marijuana users continue use during pregnancy, with many women believing that use is relatively safe."

"Due to possible adverse effects of marijuana on the fetus, ACOG recommends that marijuana should be avoided during pregnancy."

"Human fetuses exhibit the cannabinoid receptor type 1 in the nervous system as early as 14 weeks of gestation, and animal studies suggest cannabinoid exposure may lead to abnormal brain development. As reported by de Moraes Barro and colleagues, babies born to adolescents who used marijuana during pregnancy have shown adverse neurological behavior effects of the newborns in the first 24 to 78 hours after delivery."

"THC is excreted in breast milk, according to Davies, et al. ACOG recommends that marijuana use be discontinued during breastfeeding."

Children's health

"Experts note that marijuana use in the young can lead to abnormal brain development. Frequent use of high-potency THC over extended periods of time suggests that there can be negative effects on learning, memory, attention and problem-solving ability, as reported in Pediatrics in October 2017. The AAP suggests that doctors urge parents not to use marijuana around children. Other concerns with children include the potential of exposing them to secondhand smoke and accidental poisoning with edibles such as brownies or candy."

Effects on driving:

"Smoking marijuana can make driving dangerous; do not mix the two. The cerebellum is the section of the brain that controls balance and coordination. When THC affects the cerebellum’s function, drivers may have slower reaction times, impaired judgment, and problems responding to signals and sounds if driving while under the influence (DUI) of THC."

Memory and learning:

"For chronic users, the impact on memory and learning can last for days or weeks after its acute effects wear off, as noted by the NIDA."

THC remains in the body:

"THC in marijuana is strongly absorbed by fatty tissues in various organs. Generally, traces of THC can be detected by standard urine testing methods several days or more after a smoking session. In heavy chronic users, traces can sometimes be detected for weeks after they have stopped using marijuana."


"Research suggests that roughly 9 percent of users become addicted to marijuana, with higher rates if the user starts at a young age (17 percent) and in those who use marijuana daily (25-50 percent)."

"McKenna, et al have reported on the addicting potential of marijuana, noting that 'it is an erroneous belief widely held by the general public, and among many physicians, that marijuana is not addicting."


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