If you have ever wondered whether doubling your THC dose gets you higher, a new review of controlled trials has a clear answer for people who rarely use cannabis: yes, but nowhere near twice as high. Going from 5 mg to 10 mg of inhaled THC nudged the reported high up by about five points on a 100-point scale. The first 5 mg did most of the work.
The findings come from a systematic review and dose-response meta-regression led by Isabella Goodwin (Australian Catholic University) and Amir Englund (King’s College London), published in the September 2026 issue of Neuroscience and Biobehavioral Reviews. A corrigendum in the journal’s November 2026 issue removed one study from the analysis and revised the headline numbers. Some early press coverage still quotes the pre-correction figures of 41 studies and 1,020 participants. The corrected dataset is 40 studies and 983 participants, and that is what this article uses.
Key Takeaways
Across 40 randomised, double-blind, placebo-controlled trials in 983 healthy adults who used cannabis infrequently, THC reliably made people feel more high, more anxious and more tired, and less alert and less content than a placebo did. For inhaled THC, the researchers estimated that 5 mg raised the feeling of being high by 34.3 points on a 100-point scale, and the authors report that doubling the dose to 10 mg lifted it only to about 39 points, roughly a 15% gain for twice the THC. Anxiety, tiredness and alertness did not rise further with bigger inhaled doses in their model. For THC taken by mouth, the analysis found no link between dose and any of the measured feelings. The evidence comes from small lab studies, mostly in young men, and it describes how intoxicated people felt, not how impaired they were.
Doubling the THC dose: how much higher do people actually get?
Picture a volume dial that starts at zero. With a straight-line relationship, turning the dial twice as far would make the music twice as loud. THC does not behave that way in this data. The first small dose pushes the “high” a long way up the scale, and every additional milligram after that adds only a little.
Here is what the corrected meta-regression shows for inhaled THC. Each extra milligram inhaled was associated with about one extra point of “high” (the regression slope was b=1.06, p=0.0024). Because 5 mg already produces a 34-point jump over placebo, five more milligrams add only around five points. In the authors’ own words, written for a piece in The Conversation, later republished by Marijuana Moment, the high rose from 34 to 39 points when the dose went from 5 mg to 10 mg.
That pattern is common in pharmacology. Many drugs produce a strong effect at low doses and then level off, because the receptors they act on are already busy. It is a bit like a crowded train: the first few passengers change the carriage completely, and the hundredth passenger barely changes anything.
What 5 mg of inhaled THC did to six different feelings
The researchers tracked six feelings that lab studies commonly measure: high, anxious, tired, alert, calm and content. On a 100-point scale, the model estimated that inhaling 5 mg of THC changed them as follows, compared with placebo.
The feeling of being high rose by 34.3 points (95% confidence interval 30.8 to 37.7). Anxiety rose by 14.4 points (12.8 to 16.0). Tiredness rose by 26.3 points (23.8 to 28.8). Calmness rose by 4.5 points, but the confidence interval ran from minus 0.3 to 9.3, which means the result could be zero and should not be read as a real effect. Alertness fell by 40.2 points, and contentedness fell by 71.0 points.
That last number looks dramatic, and it deserves caution. Only six study samples measured contentedness, which makes it the thinnest part of the evidence. The same analysis also found that higher inhaled doses were linked to more contentedness, not less (b=1.06, p=0.025). When a small number of studies point in two directions like this, the safest reading is that the data on contentedness is not yet solid.
Bigger doses did not bring more anxiety in this model
One of the more practical findings is what did not change. For inhaled THC, increasing the dose was not associated with more anxiety (b=−0.03, p=0.845), more tiredness (b=0.39, p=0.129) or a change in alertness (b=0.11, p=0.837). Higher doses were linked to slightly less calmness (b=−0.96, p=0.048).
That does not mean a large dose is free of anxiety. The pooled comparison of THC against placebo, which mixes all doses and both routes, still showed a clear anxiety increase of 15.00 points across 28 study samples. The meaning is narrower: within the dose range these trials tested, people who rarely used cannabis already got a noticeable dose of anxiety from modest amounts, and the model did not detect it climbing steadily from there. Our earlier coverage of how CBD and THC products compared for anxiety in a longitudinal study looked at the same question in regular users outside the lab.
The authors also warned, in their article for The Conversation, that their results should not be read as evidence that bigger THC doses carry no extra risk. Frequent use of high-potency cannabis has been linked to dependence and mental health problems in vulnerable people, and conditions such as cannabinoid hyperemesis syndrome have been tied to high-potency products.
Higher doses made reactions more predictable
The review also asked a less obvious question: how much do people differ from each other? For inhaled THC, larger doses produced more consistent reactions between individuals in feeling high (b=−0.05, p=0.021) and in contentedness (b=−0.04, p<0.0001). In plain terms, at low doses some people feel a lot and others feel little, while at higher doses people’s experiences start to bunch together.
When the data from both routes was pooled, THC made feelings of tiredness less variable than placebo did. For being high, anxiety, alertness, calmness and contentedness, the spread of responses on THC was not clearly different from placebo.
Why edibles did not follow the same rule
For THC taken by mouth, which covers edibles, capsules and oils, the researchers found no meaningful link between dose and any measured feeling. The slopes for high (b=1.33, p=0.165), anxiety (b=2.24, p=0.087), tiredness (b=−1.10, p=0.448) and alertness (b=0.22, p=0.760) were all statistically indistinguishable from zero. There was not enough oral data to model calmness or contentedness at all.
The study does not prove that oral dose is irrelevant. It shows that, across 18 oral studies with different products and fasting rules, the data was too scattered to draw a dose line. The trial table itself hints at one reason edibles are harder to judge: oral studies recorded peak effects anywhere from 90 to 240 minutes after dosing, while many inhaled studies saw the peak within 15 to 30 minutes. A slow, unpredictable climb is exactly what makes “taking a bit more” with edibles risky.
There was also a split for alertness. When the analysis was separated by route, inhaled THC reduced alertness compared with placebo, while oral THC slightly increased it. Two routes, two different profiles, which is another reason not to treat a milligram eaten as the same thing as a milligram inhaled.
What this means if you grow or buy high-THC flower
Growers and shoppers often treat THC percentage as the headline number. This review measured something different: the dose that actually reached the participants, in milligrams. Those two things are linked but not the same. On paper, a gram of 20% THC flower contains 200 mg of THC, yet how much of that ends up in the body depends on how the flower is smoked or vaped, how deeply someone inhales and how much they consume.
The included trials show how wide that range can be. One smoked-cannabis study gave participants joints containing up to 69.4 mg of THC, while several vaporiser studies used 2 to 8 mg. Another trial compared smoked and vaporised cannabis in infrequent users at the same doses and found that the delivery method itself shaped the experience.
People do not always adjust well to stronger products either. A 2021 review of dose titration found only limited and mixed evidence that users cut back their intake enough when switching to higher-potency cannabis. In a Colorado study of regular users, people who used concentrates had more than twice the blood THC levels of flower users after use, yet their measured impairment was broadly similar, which points to tolerance as a major factor.
For a grower chasing ever-higher potency, the dose-response curve is a useful reality check. If the high flattens after a modest dose for occasional users, a jar of 30% flower does not deliver a proportionally stronger experience than one at 18%. It mostly makes it easier to overshoot. Label accuracy adds another layer of uncertainty, as a Massachusetts audit of THC potency labels showed. Anyone making their own edibles also has to account for decarboxylation, the heating step that converts THCA to THC, which does not always go as neatly as expected, as lab work on decarboxylation in hemp flower found.
Where the 5 mg standard THC unit fits in
The 5 mg figure in this research is not random. In 2020, two of the review’s co-authors, Tom Freeman and Valentina Lorenzetti, proposed a “standard THC unit” of 5 mg for all cannabis products and routes, similar in spirit to the alcohol unit. In 2021, the US National Institute on Drug Abuse adopted 5 mg as the standard unit for federally funded research, while stressing that it is a unit of measurement for science, not a consumption limit or recommendation.
The new review adds a practical observation to that debate. For people with little cannabis experience, a single 5 mg unit inhaled already produced a substantial high, along with measurable anxiety and drowsiness. That supports the long-standing harm-reduction message “start low, go slow,” which the authors themselves endorse.
How strong is this evidence?
This is the most comprehensive synthesis of controlled lab data on THC’s subjective effects to date, but it has real limits, and they matter.
The trials were small. Sample sizes ranged from 7 to 64 people per study arm. Participants were young, with average ages between 20.8 and 30.0 years, and 70.2% were men. Everyone included used cannabis rarely, defined as less than twice a week and fewer than 100 times in their life, so the results may not apply to regular users who have built tolerance.
The studies were also very different from each other. Some used synthetic THC, others herbal cannabis; some participants smoked, others vaporised or swallowed capsules; questionnaires and lab settings varied. The authors reported signs of possible publication bias for alertness, tiredness and contentedness, meaning studies with certain results may be missing from the literature.
Finally, the review measured how intoxicated people felt, not how well they performed. Feeling less high is not the same as being less impaired, and nothing here says that memory, coordination or driving ability level off the way the subjective high does. The corrigendum removed one trial because it used a pain-induction task that broke the study’s own inclusion rules; the authors state that the overall interpretation did not change.
FAQ
It depends heavily on experience and route. In this review, inhaling 10 mg produced only a modestly stronger high than 5 mg in people who rarely used cannabis, but 5 mg alone already raised the high by about a third of the scale and increased anxiety and tiredness. For edibles, the review could not link dose to effect at all, and oral THC took between one and a half and four hours to peak in the included trials, which makes 10 mg harder to judge.
It matters, but less directly than many people assume. Percentage describes how much THC is in the product; the effect depends on how much reaches your body, which varies with technique, amount used and tolerance. Doubling the potency of flower does not double the high, and with this dose-response pattern it mainly raises the risk of taking more than intended.
There is no official consumer definition. In research, 5 mg is the standard THC unit used by the US National Institute on Drug Abuse to compare studies, and it is often treated as a modest dose. This review shows that even that amount, inhaled, produced clear effects in infrequent users, so “low” is relative to the person.
Yes, but they come from several layers. Adult-use cannabis is legal only under state law, and states set their own rules for serving sizes and package limits on edibles. At the federal level, state-licensed medical marijuana and FDA-approved marijuana products were moved to Schedule III in April 2026, while a decision on rescheduling all marijuana is still pending; other marijuana remains in Schedule I. For hemp-derived products, a new federal definition limits finished products to 0.4 mg of total THC per container from December 11, 2026, after Congress delayed the original November 12 start date.
Legal disclaimer
This article is for informational and educational purposes only. It summarises published scientific research and does not constitute medical, legal or dosing advice. Cannabis laws differ between US states and countries and change frequently; the possession, sale and use of cannabis may be illegal where you live. The research described involved healthy volunteers in controlled settings, and its results may not apply to you. Speak to a qualified healthcare professional before making any decision about cannabis use, especially if you take medication, are pregnant or have a history of mental health conditions. Never drive or operate machinery after using cannabis.
