- Most healthy adults can use cannabis safely, but adolescents are at much higher risk of negative impacts and frank addiction.
- Understanding the early warning signs of using too much, or too often, helps you use cannabis sagely.
- 20 questions and explanations will test how safely you are using cannabis.
Most healthy adults who first used cannabis at age 18 or older never experience significant problems from the drug. Safe use of cannabis can be defined in terms of avoiding both subtle lingering changes in brain function and/or frank addiction. Only around 9 percent of adults ever meet the criteria for cannabis use disorder at any point in their lives, compared to a 15.4 percent rate for alcohol).  It is likely that even fewer cannabis users would experience any negative effects if public education about how to use cannabis safely was more widely offered.
Unfortunately, adolescents who begin using cannabis while their brains are still developing are at a much higher risk of being negatively impacted by cannabis. Fully 43 percent of those who start using at age 13 will experience cannabis use disorder at some point before they reach 30.  Although only 15 percent are still addicted at age 30, most continue to be affected by disruptions to their education and psychological maturation. The younger someone is when they begin using cannabis, the less likely it is that they will use cannabis safely.
Safe use of cannabis depends on not using high-concentration cannabis products, especially those that are low in CBD. Safety also depends upon giving the brain intervals of freedom from cannabis in order to re-establish its normal chemical balance. In other words, daily or near-daily use is far less safe than less-frequent use.
An additional strategy for safe use is to understand the earliest warning signs that you are using too much, or too often. Since every one of us has a unique brain, with its unique set of sensitivities and resilience, no firm guidelines can be given for how much cannabis is too much or what frequency of use is too often. Cannabis is not like Tylenol, where a clear upper limit is established, and every healthy adult can be confident they are safe below that limit. With cannabis, each individual must learn their own safe limit.
The following 20 questions and explanations may help you determine whether you have been using cannabis safely. Although you can test yourself without changing your cannabis use, the ideal test would follow 1-2 weeks of no cannabis use.
When not using cannabis, do you experience...?
- Nervousness or anxiety.
- Difficulty relaxing, feeling stressed.
- Physical restlessness or fidgetiness.
- Boredom or difficulty staying interested in anything.
- Reduced appetite or lower interest in eating.
- Repeated thoughts about cannabis.
- Do you use cannabis at night to get to sleep?
- Do you need cannabis at night to get to sleep?
- Do you use cannabis in the morning to get going?
- Has your cannabis use caused unhappiness for your significant others?
- Have you lost or avoided any activities or friends because of your cannabis use?
- Do you use cannabis alone?
- Do you have more difficulty finding or remembering things when you're not high?
- Have you ever hidden or minimized your cannabis use?
- Have you ever thought about cutting down, or stopping, your cannabis use?
- If you have ever chosen a period of abstinence, did you use cannabis before completing it?
- Have you ever driven when high?
- Have you ever driven after using both cannabis and even small amounts of alcohol?
1 through 8. The first 8 items are early warning signs that your cannabis use is continuing to have an impact well after the high has faded. (For more, see "5 Signs of Using Cannabis Too Frequently" and "How Cannabis Defeats Itself When Used Too Frequently.")
9 and 10. Some people enjoy the reveries cannabis evokes before falling asleep; some people are unable to sleep without cannabis; some people have an underlying sleep disorder; and some people diagnose themselves with a sleep disorder when cannabis use itself is causing insomnia. Proper medical evaluation may be in order.
11. Signs of withdrawal can occur when THC levels in the brain fall overnight.
12. Too much cannabis use can blunt sensitivity to subtle emotional cues, which is often frustrating for family members and friends.
13. For some people, cannabis use can become the central organizing principle of their life.
14. Social use can grease interactions with others, while using alone is often for other psychological reasons.
15. Memory glitches are the most common complaint of heavy cannabis users even when not high.
16. If you are hiding the level of your cannabis use from others, or even from yourself, you already suspect you may have a problem.
17. If you have thought of stopping, it's likely that you not only suspect a problem but are getting ready to be honest enough with yourself to take action to check it out.
18. If you did not stop cannabis use as long as you had planned, this may mean you can no longer control your use, although you probably fully rationalized starting again. (For more, see "2 Sources of Cannabis Addiction.")
19. Driving under the influence of cannabis involves some risk, for yourself and others.
20. Combining cannabis with even legal limits of alcohol greatly increases the danger of driving.
There is no standard number of “Yes” answers that grade your level of safety. Each person needs to assess for themself the comfort they have with their answers. If you did not answer “Yes” to any question, you can certainly consider yourself to be using cannabis safely.
For more, see "Test Your Science Literacy About Cannabis."
Facebook/LinkedIn image: Alexandre Laprise/Shutterstock
 J. C. Anthony, et al. Comparative Epidemiology of Dependence on Tobacco, Alcohol, Controlled Substances, and Inhalants: Basic Findings From the National Comorbidity Survey. Experimental and Clinical Psychopharmacology, 1994; 2(3): 244–68.
 Personal communication with John Horwood, re: Christchurch Health and Development Study Data, October 18, 2018