Before we dive in, let’s clear up a point that causes a lot of confusion.
Cannabis is the plant. Marijuana and hemp are basically the same species, but marijuana has been bred to have more resin-rich flowers, cannabinoids, and terpenes (and thus have a much higher THC content, anywhere from 5-30%), while hemp is the industrial version of the plant that has been bred more for fiber, seeds, and oil, which have a naturally lower THC content (less than 0.3%)—big difference!
So science doesn’t distinguish between them that much as a plant, but boy, the law sure does. Marijuana is a Schedule I controlled substance at the federal level, while hemp extract is a legal agricultural commodity that can be purchased over the counter.
THC and CBD are two different compounds found in that plant, and they don’t affect the body in the same way.
Here’s a handy table for comparison: (I used Claude to generate this for me)
Feature | CBD (Cannabidiol) | Hemp Extract | THC (Tetrahydrocannabinol) |
|---|---|---|---|
What is it? | A naturally occurring compound found in cannabis and hemp plants. | An extract made from the hemp plant that may contain CBD plus other plant compounds. | A naturally occurring compound found in cannabis that causes intoxication. |
Produces a “high”? | No. | Usually no, but it depends on how much THC is present. | Yes. |
Common reasons people use it | Anxiety, stress, pain, inflammation, sleep support. | General wellness, relaxation, pain, sleep, or stress support. | Relaxation, pain relief, appetite stimulation, recreation, or medical use. |
May affect driving? | Research suggests little to no impairment at typical doses studied. | Usually little impairment if THC-free, but effects depend on the product’s THC content. | Yes. Can impair reaction time, attention, coordination, and judgment. |
Can contain THC? | Pure CBD products should not, but some products contain trace amounts. | Yes. Hemp extracts may contain small amounts of THC unless specifically removed. | THC is the active ingredient itself. |
Legal status (U.S.) | Generally legal if derived from hemp and containing less than 0.3% THC, though laws vary. | Generally legal if derived from hemp and containing less than 0.3% THC, though laws vary. | Varies by state; federally illegal except in approved forms. |
Drug test risk | Low with pure CBD, but not zero. | Moderate, depending on THC content. | High. May trigger a positive drug test. |
Many autistic teens, adults, and parents have told me some version of the same thing over the years.
CBD helps.
THC helps.
Marijuana helps.
Whatever word they’re using, the message is remarkably consistent. They sleep better. Their anxiety quiets down. They feel less overwhelmed. Their sensory system finally stops acting like every sound, light, smell, and texture is a five-alarm fire.
For some people, cannabis has been genuinely helpful.
As we wrap up Chapter 3 on Potentially Driver-Impairing medications, we’ve saved one of the most complicated conversations for last. Cannabis doesn’t fit neatly into the categories we’ve been discussing.
Let’s start with why people use it.
Many autistic people report they use cannabis to help manage anxiety, sleep difficulties, chronic pain, sensory overload, muscle tension, or the simple exhaustion that comes from functioning in a world that often feels overwhelming. Some describe feeling more social. Others say they’re finally able to think more clearly. Some tell me it’s the first thing they’ve found that takes the edge off years of constant stress.
THC, the psychoactive component in cannabis, can affect reaction time, attention, coordination, decision-making, depth perception, and the ability to divide attention between multiple tasks.1,2 And—you know this—driving happens to require all of those things at once.
Many people don’t feel intoxicated. They don’t feel out of control. They may even feel more relaxed and focused than usual. But driving research repeatedly shows that people can experience measurable decreases in driving performance even when they believe they’re driving normally.3
Researchers have also found that THC-related driving impairment is usually strongest during the first hour after use, but measurable effects can remain for four to five hours after smoking or vaping cannabis.1
CBD is a different situation, at least based on current research. In the studies reviewed so far, CBD by itself showed little evidence of impairing driving performance.3,5 That’s encouraging, but there is a catch. Many products marketed as CBD contain small amounts of THC. Hemp extracts may also contain THC. Sometimes the label tells the whole story. Sometimes it doesn’t.
As usual, ask yourself how you feel after taking it: Do you seem sluggish? More distractible? Tired or foggy?
The legal realities can really bite you in the ass with any of these products. Driving while impaired by THC is illegal, even in states where cannabis itself is legal. The challenge is that THC doesn’t behave like alcohol. Detectable THC can remain in the body long after the feeling of being high has disappeared. Researchers are still debating how accurately THC levels reflect actual driving impairment. The law, however, may not care about that distinction.
Depending on where you live, a traffic stop involving suspected cannabis impairment could lead to roadside testing, blood testing, criminal charges, fines, license suspension, increased insurance rates, mandatory education programs, or other consequences. And you don’t need anything like that on your record.
So here’s my take: If you’ve recently used a THC-containing product and you’re not completely sure whether you’re impaired, wait it out. You’ll get there when you get there.
Want to See the Research?
- McCartney D, Arkell TR, Irwin C, McGregor IS. Determining the magnitude and duration of acute Δ9-THC-induced driving and cognitive impairment: A systematic and meta-analytic review. Neuroscience & Biobehavioral Reviews. 2021;126:175–193. doi:10.1016/j.neubiorev.2021.03.008
- Metrik J, Bush N, Gunn RL, McCarthy DM. Recent Advances in the Science of Cannabis-Impaired Driving. Current Addiction Reports. epub-ahead-of-print 2026;13(1):8. doi:10.1007/s40429-025-00712-0
- Arkell TR et al. Driving Performance and Cannabis Users’ Perception of Safety: A Randomized Clinical Trial. JAMA Psychiatry. 2022;79(3):201–209. doi:10.1001/jamapsychiatry.2021.4037
- McCartney D, Suraev A, McGregor IS. The “Next Day” Effects of Cannabis Use: A Systematic Review. Cannabis and Cannabinoid Research. 2023;8(1):92–114. doi:10.1089/can.2022.0185 (not cited above, but helpful information, imo)
- Arkell TR et al. Effects of Cannabidiol on Simulated Driving and Cognitive Performance: A Dose-Ranging Randomized Controlled Trial. Journal of Psychopharmacology. 2022;36(12):1338–1349. doi:10.1177/02698811221087641