The short answer is that you can’t tell for sure, but you can look out for certain signs.
The place to start would be to ask your friend if they feel like their use is unhealthy, or if it’s getting in the way of some of their goals. There might be something you don’t know about why they’re using, so visible indicators of heavy use – using every day or almost every day, using a lot (e.g., more than 1-2 grams a day), using before noon or even right away when they wake up – will not always indicate use that is problematic.
Instead, people trying to examine problematic use from the outside, like clinicians or researchers, will ask questions like “Is your cannabis use causing you problems?” or “Do you spend more time than you’d want to getting high or thinking about getting high?”.
Of course, this is just to give you an idea, and is not enough to establish with certainty that use is problematic. To get a better understanding of why your friend is using, you may also want to consider their main motive, as different reasons to use are associated with varying degrees of risk that someone’s cannabis consumption will become a problem for them.
For example, if your friend is using to cope with difficulties in their life, that’s associated with a higher likelihood of using problematically, but it also means they might be going through a tough time and may not have access to alternative resources they need. We talk more about different reasons to use here.
“Smoking weed is fun. No doubt about it. It also takes away anxiety and depression. But what I didn’t know is that weed can cause anxiety and depression. Not to mention psychosis, paranoia, and other nasty stuff.”
Finally, there’s also the concern about cannabis addiction, which certain researchers may refer to as cannabis dependence. People who are dependent on cannabis will often experience withdrawal symptoms when they stop using, such as anxiety, a strong sense of uneasiness, sleep disturbances, irritability, loss of appetite and in some cases, aggressive behaviour. If you think this might be the case for your friend, we’ve got more information on cannabis dependence here.
“At the same time I don’t like how it makes me feel afterwards even if it cheers me up. I lose my motivation for the day, kinda similar to a hangover… I go through ups and downs, I feel pretty good, laughing, having a good time… then I start worrying about things and I get tired too”