Frequently Asked Questions about Cannabis

Washington State University researchers have compiled the following list of frequently asked questions about cannabis and cannabis use for the general public to increase awareness and overall knowledge.

Disclaimer:  WSU does not promote the use of marijuana, cannabis, or other related products for the treatment of any medical conditions. Consuming marijuana (cannabis) may impair judgment, motor coordination, and reaction time.  See National Institute on Drug Abuse.  The decision to use cannabis for medical purposes is best made between patients and their health care practitioners who are treating patients for specific conditions.  Marijuana (cannabis) is a Schedule I controlled substance under Federal law.   See Drug Enforcement Agency Drug Schedules.  Each state regulates marijuana (cannabis) differently.   It is important to check your state laws when considering medical treatment involving the use of marijuana (cannabis). 

This Q&A contains questions WSU researchers are frequently asked and is not a recommendation for the use of marijuana, cannabis, or other related products. Please speak to your health care provider for specific questions about your own medical conditions if you use or plan to use any marijuana or cannabis-based products.

Hemp and cannabis (also called high-THC cannabis, adult use cannabis, or marijuana) are different versions of the same species, Cannabis sativa. The major psychoactive component in C. sativa (both cannabis and hemp) is delta-9-tetrahydrocannabinol or THC. Hemp is defined as C. sativa that has 0.3% or less THC, meaning that hemp products don’t contain enough THC to create the “high” traditionally associated with cannabis – assuming those products are not refined so that they have elevated levels of THC. Hemp is used for many purposes, from medicinal applications (CBD, see below) to food (hemp seed or hemp “hearts”) to industrial/building applications (fiber and seed-derived products). In contrast, cannabis – defined as C. sativa containing more than 0.3% THC – is used for its medicinal value (see below) and for recreational purposes due to the “high” that THC produces when consumed.

Placebo-controlled clinical trials have found that cannabis may relieve pain in some people, but its pain-relieving effects appear to be very limited1,2, and tolerance may develop if cannabis is used frequently at higher doses3,4.   It is not yet clear whether cannabis works better than other options – including non-drug interventions – to manage pain.


  1. Stockings et al. (2018)
  2. Mücke et al (2018)
  3. Colizzi & Bhattacharyya (2018)
  4. Singla & Block (2022)

Cannabis may be effective for some medical conditions in some individuals, and when low-to-moderate doses are used, cannabis produces fewer, milder side effects and has fewer safety risks compared to opioids, especially for adults (if pregnant or breastfeeding, see Q4 below).  One primary difference between cannabis and opioids is that cannabis does not depress the respiratory centers in the brain like opioids do, so lethal overdose on cannabis is highly unlikely.  However, in clinical trials, cannabis/cannabinoids produced more “non-serious” side effects than did placebo; most commonly reported were drowsiness/fatigue, dry mouth/thirst, and nausea/vomiting1,2.  Cannabis does impair driving, even when users may not feel impaired3 (see Q7, below).  When used frequently at higher doses, cannabis can be addictive (see Q4 below), can occasionally cause “cannabinoid hyperemesis syndrome”, a disorder characterized by recurrent abdominal pain and nausea/vomiting4, and may increase risk of heart disease5.  Health risks may be greater for older adults (≥ 65), perhaps due to the higher baseline rates in older compared to younger individuals of falling, mental confusion, and cardiovascular events, all of which cannabis can exacerbate6.


  1. Wang et al. (2008)
  2. Aviram et al. (2022):
  3. Marcotte et al. (2022):
  4. Burillo-Putze et al. (2022)
  6. Han et al. (2023)

Cannabis is not recommended for pregnant or breastfeeding women by the American College of Obstetricians and Gynecologists1, because fetuses and infants are exposed to cannabis that their mother consumes via the placenta and through breastmilk; this exposure may negatively affect the developing brain of the fetus and infant 2.  Prenatal cannabis exposure has been found to increase the risk of preterm birth and low birth weight3.  Additionally, cannabis use during pregnancy has been associated with impaired memory, attention, and impulse control, plus increased experience of psychotic symptoms in children, which may persist into adolescence2,4.


  2. Scheyer et al. (2019)
  3. Luke et al. (2022)
  4. De Genna et al. (2022)

Substance use disorder (“addiction”) is a chronic, relapsing disorder characterized by compulsive drug-seeking and use despite harmful consequences (e.g., to health, relationships, work/school performance); it is associated with long-lasting changes in the brain.  It is currently estimated that 1 in 5 cannabis users develop cannabis use disorder, with more frequent use of higher THC-containing products increasing the risk of developing cannabis use disorder1.  Frequent use of high-THC containing products typically causes tolerance to the desired drug effects due to compensatory changes in the nervous system.  However, only about half of regular cannabis users experience withdrawal when they stop or reduce cannabis use2, with the most common symptoms being negative mood changes (anxiety, irritability, anger, depression), disturbed sleep, and appetite loss.  These symptoms can lead to relapse in some people.


  1. Robinson et al. (2022)
  2. Connor et al. (2022)

Use of cannabis by teens and young adults under 21 is illegal.  There is a growing scientific literature demonstrating long-term health risks of cannabis exposure in youth, whose brains and bodies are still developing at a rapid rate.  The endocannabinoid system is crucial to the development of connections and pathways in the brain, thus use of cannabis can alter brain development.  Alcohol is indeed acutely (immediately) more impairing than cannabis (e.g., leading to a higher rate of accidents and overdoses), and heavy alcohol use has more severe long-term health effects than heavy cannabis use.  However, frequent adolescent use of high-THC products that are commonly available today has been linked to a higher rate of psychosis and suicide, plus impaired thought-processing later in life1,2.    


  1. Tirado-Munoz et al. (2020)
  2. Hurd et al. (2019)

Cannabis affects areas of the brain that control speed of movement, attention, thought-processing speed, and judgment.  Thus, cannabis use can impair skills required for safe driving by slowing reaction time and decreasing the ability to make quick decisions.  Controlled clinical trials demonstrate that smoked or vaporized cannabis impairs driving for several hours – despite the fact that a majority of drivers believe they can drive safely by 1.5 hours after cannabis use1.  The primary impairments are increased weaving and decreased driving speed2.  It is currently unclear whether tolerance to cannabis in daily users is sufficient to decrease risk of motor vehicle operation.  Driver impairment has been observed at moderate to high concentrations of THC, with or without CBD, although high-CBD/low-THC cannabis has not been found to be significantly impairing3,4.  THC-dominant cannabis and alcohol used together produce additive impairment, significantly increasing the risk of fatal crashes2.


  1. Marcotte et al. (2022)
  2. Simmons et al. (2022)
  3. Arkell et al. (2019)
  4. Arkell et al. (2020)

Common cannabis and cannabinoid product contaminants include microbes, heavy metals, and pesticides1, as can be the case for any plant-based product.  Washington State requires that all cannabis products sold legally through the state’s regulated market be tested for common or concerning types of contaminants.  WA State quality control testing requirements for cannabis products can be found at WAC 314-55-102, Cannabis obtained on the unregulated (“black”/illegal) market is not under the purview of state regulators and therefore may not be tested for such contaminants. Not all states have the same requirements for quality control and accurate labeling as WA does.


  1. Dryburgh et al. (2018)

Delta-8-THC produces a “high” and other effects that are very similar to those produced by delta-9-THC1,2.  Delta-8-THC naturally occurs in trace amounts in both hemp and high-THC cannabis plants, but manufacturers have figured out how to produce it from a third notable chemical in cannabis plants, CBD.  CBD is present in large quantities in some hemp varieties, and because CBD is legal, these producers have asserted that delta-8-THC is as well.  However, the Drug Enforcement Agency (DEA) announced in February 2023 that delta-8-THC and other synthetically derived cannabinoids are schedule 1 controlled substances that are not legal to either produce or sell.  If it is extracted from hemp or high-THC cannabis, and not generated by chemical transformation/synthesis, delta-8-THC remains legal according to the DEA.


  1. Tagen & Klumpers (2022)

In 2018, the U.S. Congress passed and signed into law the Agriculture Improvement Act. This law removed hemp from the federal Controlled Substances Act.  Therefore, as long as it is extracted from hemp, CBD is a legal substance.  However, the only FDA-approved CBD medication is Epidiolex, which may be prescribed for childhood seizure disorders.  That is, only CBD in the form of Epidiolex is scientifically validated in terms of efficacy for certain seizure disorders1, and it is the only form of CBD that is regulated – meaning that only this form of CBD is subject to strict quality control and accurate labeling requirements.  In other words, when it comes to retail CBD products, “buyer beware”.  Retail CBD products have been found to vary dramatically in actual CBD (and THC) content2, and some CBD products have even been found to contain other, potentially harmful substances3

It is not yet known what daily dosages of CBD are effective for other medical conditions.  There is some placebo-controlled, clinical trial evidence suggesting efficacy of higher doses of CBD for some types of anxiety, but there is no compelling scientific evidence that CBD is effective for any other medical conditions; however, very few high-quality studies have been completed4.  Numerous safety studies indicate that up to relatively high daily oral doses, CBD produces no serious adverse effects in the short-term (up to 3 months of daily use), with the most common non-serious adverse effects being sleepiness and diarrhea3.  Hundreds of clinical trials are underway to evaluate CBD’s efficacy for a range of medical conditions; details can be viewed here:


  1. Reddy (2023)
  2. Johnson et al. (2022)
  3. Poklis et al. (2019)
  4. Arnold et al. (2023)

THC, the psychoactive ingredient in cannabis, interacts with nearly 400 prescription medications, and CBD (cannabidiol) interacts with even more.  This is because THC and CBD affect several enzymes that our liver uses to metabolize many common medications; the result can be a decrease in the effectiveness of the medication, or an increase (possibly causing overdose)1,2.  Common types of drugs that cannabis (THC or CBD) can interact with include:

  • Hypnotics and sedating drugs — such as zolpidem (Ambien), eszopiclone (Lunesta), and diphenhydramine (Benadryl)
  • Anti-anxiety medications — such as alprazolam (Xanax) and diazepam (Valium)
  • Anti-depressants — such as sertraline (Zoloft), fluoxetine (Prozac), and escitalopram (Lexapro)
  • Pain medications — such as opioids (e.g., Oxycontin, Vicodin), including methadone and buprenorphine used to treat opioid use disorder
  • Anticonvulsants (anti-seizure medications) — such as carbamazepine (Tegretol), topiramate (Topamax), and valproate
  • Anticoagulants (blood thinners) — such as warfarin (Coumadin) and heparin

If you take any prescribed OR over-the-counter medications and wish to use a THC- or CBD-containing product, check with your health care provider FIRST to determine whether such a product could interfere with your medication(s).


  1. Antoniou et al. (2020)
  2. Bardhi et al. (2022)
  3. Kocis et al. (2023)

Medical cannabis for personal use must be authorized by a Washington licensed health care professional for a qualifying medical condition.

The process for becoming a medical cannabis patient in Washington State is:

  • Step 1: Schedule an appointment with your health care practitioner.
  • Step 2: Obtain a medical cannabis authorization from your practitioner.
  • Step 3: Visit a medically endorsed store to get a medical cannabis card.
  • Step 4: Use the card to purchase products sales tax free.
  • Step 5: Repeat steps 1 – 4 to renew both the medical cannabis authorization and card before expiration.