The ABCs of CBD, THC, Medical Marijuana, and More

The Brain on Cannabis

Some people believe all forms of marijuana will hurt you, while others insist they’re perfectly safe. With so much conflicting information, it’s hard to know what to believe about this increasingly available substance that, over the decades, has transitioned from its status as a common recreational drug to becoming a segment of mainstream medicine.

Increasingly, people are asking healthcare providers about the use of marijuana and its derivatives for certain health problems. However, since the research is still ongoing, getting a clear answer has been difficult. Enter Rebecca Siegel, MD, a psychiatrist with Amen Clinics New York, who provides clarity on the subject.

Inspired by the questions she was fielding from her own patients, Dr. Siegel began exploring the pros and cons of cannabis, along with studying its medicinal uses. She eventually earned a certification that allows her to certify her patients to obtain state-regulated marijuana for certain health conditions. Since that time, she has discovered a great deal more and recognizes how complicated, confusing—and often inaccurate—the available information can be.

Getting to Know The Brain on Cannabis

In a genuine effort to help others understand the background, uses, myths, and research about marijuana for medicinal and recreational uses, Dr. Siegel has written a fascinating new book entitled, The Brain on Cannabis: What You Should Know about Recreational and Medical Marijuana (release date September 28, 2021). In an easy-to-understand manner, she covers both sides of the marijuana debate as well as shares factual information that can empower readers with the knowledge to make their own decisions about whether or not to choose medical marijuana—or related products for recreational use.

One of the most helpful things about this book is that Dr. Siegel begins with the basic information about marijuana, including descriptions of the terminology that so often confuses people. For example, she explains that the flowers and leaves of the plant, cannabis sativa, are what marijuana is made from. There are also varieties of the cannabis plant known as hemp, which is not taken as a drug. Instead, it has strong fibers that are used to make rope, paper, and fabrics.

What Differentiates CBD and THC?

Another piece of foundational information Dr. Siegel discusses in her book are two of the most well-known compounds—CBD and THC—that are frequently misunderstood. She explains that CBD, which stands for cannabidiol and is best known for its medicinal properties, is non-psychoactive. This means it doesn’t produce the mind-altering effects, i.e. “feeling high.” And according to a research study in the journal, Trends in Pharmacological Science, it is not considered to be a toxic or impairing substance.

Conversely, tetrahydrocannabinol—or THC—is the part of the cannabis plant that usually induces a mildly euphoric feeling for most users, although it can affect people in different ways—some of which are not good. Research continues to be ongoing about the adverse impacts of THC on the brain, especially for young people and those who may be genetically vulnerable to mental illness. Brain SPECT imaging studies conducted at Amen Clinics show that marijuana users have lower blood flow in areas of their brain that are associated with memory and learning.

Research continues to be ongoing about the adverse impact that THC from the cannabis plant has on the brain, especially for young people and those who may be genetically vulnerable to mental illness. Click To Tweet

Despite this, it may be surprising to learn that THC is not only used for recreational purposes, but it actually has medicinal properties too.

Medical Uses of Marijuana and CBD

With her extensive clinical experience and the scientific lens through which she stays current on developments about the medicinal uses of CBD and marijuana, Dr. Siegel has been able to help many patients. In an excerpt from her book, she writes:

“In my practice, I’ve seen patients with a variety of conditions— most frequently, chronic pain, PTSD, inflammatory bowel disease, and cerebral palsy—benefit from medical marijuana. Evidence has also revealed that medical marijuana has been proven to alleviate pain, discomfort, and nausea associated with the effects of some cancer treatments. And the use of medically approved CBD has had remarkable results in children suffering from countless daily epileptic seizures. Scores of other patients will testify to the ways it has benefited them.

Although most medical professionals agree that more research is needed to fully understand how marijuana in general, and THC in particular, affect the brains and bodies of users, it is already providing hope for many.”

Throughout The Brain on Cannabis, Dr. Siegel addresses both sides of the marijuana debate, and dispels the myth that marijuana is always harmful or always harmless. She believes neither of these are true; that in fact, marijuana can be harmful to the brain AND it can be useful for medical purposes. This new book equips the reader with the best information available at the time of its writing so they can make smart choices about marijuana for themselves.

CTA: If you’re seeking validated information about the potential benefits and risks of marijuana, Rebecca Siegel, MD, a psychiatrist and certified prescriber of medical marijuana has written a comprehensive guide that addresses both sides of these issues. With a relatable style and easy-to-understand language, The Brain on Cannabis: What You Should Know about Recreational and Medical Marijuana, clarifies the confusion around the ever-evolving discussions on marijuana and its appropriate uses. Click here to order your copy now.


  1. What are the findings on CBD? As in CBD drinks and gummy bears etc.

    Comment by Amanda — September 24, 2021 @ 4:13 AM

  2. (Years ago I tried pot a few times recreationally.
    I am a highly sensitive person/empath. I felt paranoid almost immediately and also noticed memory loss, and an inability to visualize after a very short time. My reaction to it was a painful slow down of thinking while on it which was very uncomfortable. I therefore realized I was not able to smoke pot and haven’t done drugs of the recreational kind since. I have believed it did damage to my brain.

    Comment by Cecila — September 24, 2021 @ 5:22 AM

  3. Over the years I have wondered if my marijuana use in my youth have had an effect on my children’s mental health? Even after discontinued use and never during pregnancy. In my experience marijuana helped me overcome anorexia .

    Comment by Christine — September 24, 2021 @ 6:24 AM

  4. I am eager to read more. So far, microdosing THC and the neuroplasticity of cannabis haven’t been discussed by Amen Clinics. Certain strains stimulate certain types of cognition and make users more alert and adaptable. I think there are nuances that need to be explored.

    Comment by Jezebel J. Pancia — September 24, 2021 @ 6:52 AM

  5. About time there were some pragmatic analyses about CBD and THC derivatives. There was a largely pointless “war on drugs” fomented by conservative political elements in the USA, based originally upon racist mentality in the early 20th century which not only wasted huge resources, but criminalized an entire potentially legit industry. As the article points out, hemp has been a good sewing and building material for centuries. THC helped my brother to deal with cancer pain and chemo side-effects during his hospice. CBD was not commonly available yet, but he would have likely preferred it.

    And the “war on drugs” discouraged legit medical research on the above substances, which have since obviously distinguished themselves as useful for pain management as well as some CNS disorders. The people who enthusiastically
    backed the “war on drugs” and personally benefitted from such misdirected efforts, deserve to be fully excoriated.

    Comment by Tracy Avent-Costanza — September 24, 2021 @ 7:18 AM

  6. This book is needed. I am 80 yr old and have chronic nerve pain. Even though it was against the law I started using 1 yr ago. for pain at night. 5 mg and 1 repeat as needed. I am up less, 4-5 to 1=2, A1C now normal, need less sleep due to better sleep. When I occasionally need help during the day there are no mental side effects. I use Indica. Properly used it is a wonderful natural medication. Anything can be abused and used wrong I used to use cbd for diabetes. It wasn’t as good for the pain. It is hard to overcome the bad press and prejudice of me friends.

    Comment by Martha Petty — September 24, 2021 @ 9:54 AM

  7. I am a 64 year old woman, ADD/ADHD who has self medicated on drugs and alcohol my entire adult life. I have been sober for 26 years and one of the scariest things for me to think about when I first got sober was…smoking Pot. I have so many friends and family members who smoke daily from morning till night and insist they don’t have a problem/addiction and it makes me wonder, sure seems like an addiction to me?? Also it is often said that Marijuana is not a gateway drug. I disagree and was wondering about your thoughts and this

    Comment by Leigh Sandifer — September 24, 2021 @ 3:18 PM

  8. I suffered a brain injury due to a serious illness years ago. My neurologist showed me the mess on my MRI and informed me that my brain more closely resembled that of an elderly Alzheimer’s patient than a healthy adult. I was 45 at the time. The tricky part is that she had no advice or hope of recovery so all I had was the diagnosis. I set out to investigate my options and came across studies showing that cannabis was beneficial for a variety of neurologically damaging conditions, including Alzheimer’s.
    The illness that I had had was encephalitis and I could find nothing at all to connect cannabis and encephalitis but I knew it was safe to try. I used myself as a test subject and went to work.
    Of course, during the period right after you consume cannabis, your memory is vague along with the other symptoms of being “high” so I took my dose at night before bed.
    Here I am, all these years later with a perfectly functioning brain and I don’t struggle with anxiety or depression, which were horrendous in the early years of my recovery.
    Cannabis heals. As with any medication, there will always be people who shouldn’t use it but if you’re going to use or recommend cannabis, then please be informed enough to know that different strains provide different effects. Such as, if you use cannabis and you find that you become paranoid or anxious, you are probably using a strong sativa strain so try something different, and probably one of the many indica strains which have much more relaxing effects. You can’t say “cannabis” with any specificity any more than you can say “people” and expect me to know who you’re talking about. lol Cannabis gave me my life back. Without being crippled by anxiety or depression, I was able to take on tasks that rebuilt what I had lost to the illness. I wasn’t able to walk or think or finish my own sentences. Talk about depressing!!
    Thanks to cannabis, I was able to remain relaxed and positive and do what needed to be done to rehabilitate my brain and body.

    Comment by Linda — September 24, 2021 @ 3:56 PM

  9. Well, Cecelia, I had just the opposite effect. I am an empath, but I did not feel paranoia but the opposite.

    Memory Loss however, comes from the effect that Cannabis inhibits our thinking in the ‘this is past’ mode. That can feel like ‘loss of memory,’ but is really just overriding the senses and placing someone who is “high” smack dab in the present.

    As to the visual cortex aspects — inability to visualize — I tended to hallucinate while on week. Almost to the point of a similar effect to LSD and Mushrooms. Now That seemed like paranoia to me, but was only locked in internalized visualization.

    I did not have the desired effects that I hoped for with CBD Oil however, but I do know people for whom it has worked wonders.

    Comment by Robin — September 24, 2021 @ 6:36 PM

  10. Why can’t a scan be done while using marijuana to see the effect on a person’s brain so it isn’t speculation?

    Comment by Merrie VonSeggern — September 24, 2021 @ 11:06 PM

  11. Thank you for Sharing your experience Cecilia that helps me with someone I know who is similar

    Comment by Diann Elyse Colburn — September 25, 2021 @ 4:25 AM

  12. Life without cannabis as a stage 4 cancer patient would be a living hell. It is a miracle plant for some people. Obviously it’s not for everyone but thankfully when cancer patients are going through chemo it allows them pain control appetite and mood modulation. I’m so grateful for the fact that someone can function without oppoids and other addicting drugs. We are fortunate to live in a state where it is legal and we can control the quality of the pot. It’s costly but the cost is better than the alternative like fentanyl and morphine.

    Comment by Debra — September 25, 2021 @ 4:25 AM

  13. My 22 yr old lives here in CA where Medical Marijuana is legal and very easy to access 24/7. She is now a daily smoker and the use has completely changed her personality: She’s become mean and explosive/angers easily; she’s sometimes paranoid, is manipulative to get what she wants and with only two more classes to achieve her BS degree, has abandoned the effort. She has zero friends, has been fired from all her jobs and blocked contact with all family members. The only thing all we can do is love our daughter and pray for her. So sad that a beautiful, successful and smart young woman has lost her way. As a Veteran, I know that Marijuana has amazing medical benefits but I also know that it’s use can be the opposite of positive/good and that it is a gateway drug.

    Comment by Kelly — September 25, 2021 @ 7:56 AM

  14. I smoke fir PTSD with intrusive visions, Depression severe aniexty and HUGE CHRONIC PAIN. Recovered frim Alcohol 19 yr and drugs like meth cocaine and more for 15 years. My severe head injuries TMTC have left me with all kinds of well not fun stuff. I have no credit no money to get spect and will live like this for the rest of my life

    Comment by Pamela Palmer — September 25, 2021 @ 10:04 AM

  15. I have smoked pot for most of my adult life. Really like it. I just like the buzz I get. Nothing major or like drinking but I do enjoy it and then I do chores or projects and it’s enjoyable. I am now 65…Can’t wait to read Dr. Siegel’s book when it comes out. I could always learn more about the subject and I LOVE Amen Clinic ANYTHING! Thank you for that!

    Comment by Trish — September 25, 2021 @ 12:46 PM

  16. I too am an HSP and Empath, and I use Marijuana as a medicine regularly. It helps me to relax at the end of the day from absorbing others energy. It helps slow my mind down and I get out of my own way. It actually gives me clarity and ah ha moments frequently. I respect mother nature’s gift and will continue to use it. I believe it isn’t for everyone but it certainly can help many. Know the facts, not the propaganda!

    Comment by Denise — September 25, 2021 @ 4:16 PM

  17. What caught my attention in my research on cannabis was that longitudinal studies show that about 35% of regular users develop psychosis. I personally would prefer pain to psychosis (which could cause me to hurt someone).

    Comment by Becky Brown, LMFT — September 26, 2021 @ 7:49 AM

  18. I too was a little paranoid, my dr. said that there’s a subset of people who experience this. However, keep the mindset that it is only temporary, ride through it and it will go away, and it did for me. It’s been a game changer for me w/ my chronic lyme / pain issues. I’d recommend trying it again, and you can get some that don’t have THC, just the cannibinoids, so many strains.

    Comment by Rose — September 26, 2021 @ 8:40 AM

  19. Thanks for this informative article. Yet, somewhat confusing as Dr. Amen seems to consistently argue against using it. More clarification would be awesome! Thanks!

    Comment by Sammy Adari — September 26, 2021 @ 3:08 PM

  20. My doctor prescribed the medical marijuana for my chronic pain. I was using the CBD a small amount at a time with a little THC added to it. I had to increase the amount every 3 days. I group up to the CBD at 1200mg 3 times a day and tried adding THC only at night. I never felt a change in pain regardless of how much I took. It cost me hundreds of dollars for a couple of months. Regular pain meds don’t help, only cause constipation. I give up and figure I’ll just learn to live with the pain. Any suggestions?

    Comment by June Hillyard — September 26, 2021 @ 6:45 PM

  21. I am losing hope that my pain and anxiety wk ever go away! I live in sc where it’s illegal to purchase any sort of thc! Know that there are immensful benefits from the marijuana plant tho! Any advice?

    Comment by Mac Dunbar — October 4, 2021 @ 1:22 PM

  22. When I was three months old I had to have a liver transplant during the liver transplant it was a mishap and it caused me to have brain damage . I don’t have pain but I do have a seizure disorder that is not in control with medication is there a is there anyway that you can help me with my situation. Sincerely Theodore Worth

    Comment by Theodore D Worth — January 25, 2022 @ 3:22 PM

  23. Hello Theodore, thank you for reaching out. We’d be happy to contact you directly with more information.

    Comment by Amen Clinics — January 26, 2022 @ 9:34 AM

  24. My cousin has been in and out of hospital several times this month due to his bowel discomfort. Right now, he’d consider other alternative treatments for the condition. Well based on what you pointed out, who would’ve thought that medical marijuana can help improve our digestive system too, huh? I’ll make sure he refers to a certified practitioner before consuming anything related soon.

    Comment by Amy Saunders — April 20, 2022 @ 12:27 AM

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