Switching from THC to CBD: withdrawal, saliva tests, the law

THC (Δ⁹-tetrahydrocannabinol) produces the psychoactive effect of cannabis. CBD (cannabidiol) comes from the same plant but does not. In France, THC is a narcotic; CBD can be sold freely if the finished product contains no more than 0.30% Δ⁹-THC, the limit set by the order of 30 December 2021. The Conseil d'État struck down on 29 December 2022 the ban on selling raw flowers and leaves that the order contained.

The consequence is simple: CBD is not "light THC". Anyone expecting the same high will be disappointed. Anyone who wants to keep a ritual, a flower, a smell, a gesture, without the psychoactive molecule may find what they are looking for. Our article on the differences between THC and CBD covers the chemistry of both molecules.

Cannabis withdrawal syndrome is recognised by the American classification of mental disorders (DSM-5): it is diagnosed when at least three symptoms appear within a week of stopping abruptly. The most common are irritability, anxiety, sleep problems, reduced appetite and restlessness.

It is common. A meta-analysis published in 2020 in JAMA Network Open, pooling 47 studies and 23,518 people, found it in 47% of regular or dependent users. The share varies with the setting: 17% in the general population, 54% among outpatients, 87% among inpatients.

Its timeline is well described. In a 2003 study that followed 18 users through 45 days of abstinence, symptoms began between day 1 and day 3, peaked between day 2 and day 6, and most lasted 4 to 14 days. A 2017 review puts the usual duration of the syndrome at 3 weeks at most.

Knowing that the peak falls at the end of the first week helps you not read those difficult days as a failure.

The question has been studied, and the honest answer is: not demonstrated yet. A phase 2a trial published in 2020 in The Lancet Psychiatry followed 82 adults for 4 weeks, on 400 or 800 mg of CBD a day or a placebo, alongside motivational support. With 400 mg, the authors measured less THC metabolite in urine than on placebo and half an extra cannabis-free day per week (0.48 day). With 800 mg, the gain in abstinent days was not clear.

A Cochrane review published in 2025, covering 37 trials and 3,201 participants, concludes that no medicine is approved for cannabis use disorder and that these options remain experimental. For CBD, it includes a single study of 68 people, with low-certainty evidence. An Australian phase 3 trial of 250 adults is under way.

Two points to add. The doses in these trials, 400 to 800 mg a day, bear no relation to those of products sold in shops. And the only CBD medicine available in France, Epidyolex, is prescribed for certain rare epilepsies, not for withdrawal. CBD is not a treatment for dependence: if quitting alone is hard, support remains the way forward.

If you switch to CBD, the choice of format is mostly about habit. A CBD flower keeps the gesture and the smell; a CBD oil removes combustion and is measured with a dropper. Neither is "better" for giving up THC: no data allows anyone to say so.

What matters is residual THC. The 0.30% limit allows traces: a full-spectrum flower or oil can contain some. For someone who wants to leave THC behind or who drives, an isolate or a broad-spectrum product, with no detectable THC on the lot analysis, makes more sense. Our comparison of full spectrum versus isolate and the guide to THC-free oils explain the differences.

On amounts, on 9 February 2026 EFSA set a provisional safe intake level of about 2 mg of CBD a day for a 70 kg adult, in food supplements. The agency does not give a level for people under 25, pregnant or breastfeeding women, or people on medication. The background is in our article on how much CBD per day.

Police saliva tests look for Δ⁹-THC, not CBD. Drogues Info Service sums it up: CBD without THC does not make a saliva test positive, and positive results after CBD come from the THC it contains.

Two durations are worth knowing. After a single session of smoked cannabis, a 2014 controlled study measured a median saliva positivity of 12 hours in occasional users (from 4 to 24 hours) and 21 hours in frequent users. In urine, the THC metabolite stays detectable much longer: among 86 chronic users, a 1985 study recorded 27 days on average, and up to 46 days. Switching to CBD therefore does not reset a urine test.

French law does not look at the dose. The Cour de cassation ruled on 21 June 2023 that driving after using narcotics is an offence whatever the amount taken, and that the product's compliance with the 0.30% limit makes no difference. Article L235-1 of the Highway Code punishes this offence with 3 years in prison and a €9,000 fine. The CBD and drug testing guide covers the three types of test, and the article on clearing THC from the body takes apart the methods said to speed it up.

Some products sold as "legal alternatives" to cannabis contain semi-synthetic molecules that mimic THC. They are classed as narcotics. ANSM banned HHC, HHCO and HHCP from 13 June 2023, then H4CBD, THCP and other derivatives from 3 June 2024.

For anyone trying to leave THC behind, these products are a dead end: they reproduce the effect you are moving away from, with narcotic status and an often unknown composition. Our timeline of the HHC ban and the article on synthetic cannabinoids explain how to spot them.

Quitting THC does not have to be done alone, and help exists at no cost in France.

• Drogues Info Service answers on 0 800 23 13 13, from 8 am to 2 am, 7 days a week. The call is anonymous and free.
• Consultations jeunes consommateurs (CJC) offer free, confidential appointments, mainly for 12 to 25-year-olds, and also see parents.
• Your GP can assess dependence and refer you, if needed, to an addiction clinic.