Throughout my 20s, I tried weed only a handful of times. I experimented with different strains, from indica to sativa and different forms, from joints to edibles. All of them would send me into a paranoid thought-loop.

Then, at age 29, I tried a low-THC strain, knowing it might be less likely to cause anxiety. It actually didn't make me anxious at all. A few weeks later, a friend offered me a few puffs of a very high-THC strain, which I expected would send me back into my old thought patterns — but it actually just made me feel happy and creatively inspired.

Why does weed suddenly like me? I wondered. It turns out weed can actually have a different effect on us as we age.

“I have heard from many patients and colleagues about this phenomenon of cannabis affecting them differently over the years,” says Nikola Djordjevic, physician and medical advisor for the online cannabis guide LoudCloudHealth. “It ranges from ‘nothing’s changed’ to people experiencing full-blown panic attacks and increased anxiety out of the blue.”

Evidently, the changes people experience in their reaction to weed aren’t always positive. Christopher Klein, a 32-year-old working in gym sales in Austin, says that after a decade of consistent use, cannabis no longer helps him sleep like it used to.

The most common change people see is simply increased tolerance to THC, the compound in cannabis that makes you feel high, which results in less intense effects, says Bonni Goldstein, physician, and medical director of Canna-Centers Wellness and Education, which offers potential cannabis patients medical evaluations. “Tolerance happens when the cannabinoid receptors detect too much THC over time, causing the receptors to withdraw into the cells, basically ‘hiding’ from the THC in the bloodstream,” she explains. This can also lead to increased anxiety, because it may prevent the endocannabinoid system from working to maintain balance.

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“Very heavy frequent use will down-regulate cannabinoid receptors, making the body less adaptive to stress and changing neuroendocrine environments,” explains Joseph Morgan, a physician and medical expert for the cannabis education platform Green Flower Media. Some heavy users even begin to develop Cannabis Emesis Syndrome, which is characterized by nausea and vomiting while stoned.

When people become less anxious and more relaxed on cannabis over time, on the other hand, it’s often because they’re less anxious about the weed itself, since they’re used to it, Goldstein says. In addition, THC use can — in some cases — balance out the endocannabinoid system over time in a way that reduces overall anxiety.

Sometimes, someone’s intentions or expectations when using cannabis can change its effect.

A variety of other factors like diet, stress levels, exercise, and brain injuries can also physically change the brain receptors in our endocannabinoid systems so that we process the compounds in cannabis differently, Goldstein tells Mic.

Sometimes, someone’s intentions or expectations when using cannabis can change its effect, says Morgan. That was the case for Pedro Martinez, a 37-year-old small business owner and photographer in Long Beach, California. “When I first started smoking cannabis, it was all recreational. Something to do with friends and act stupid. It made me feel pretty dumb. I still smoked it and just got silly,” he says. “Cannabis for me these days is all about getting to relax. I am more structured with it, too — I won’t smoke weed during work hours.”

Martinez’s experience expresses how the larger context of what’s going on in someone’s life can change how their high feels. “As my responsibilities became greater, cannabis had a more adverse effect on me, and it went from mellowing me out to making me a paranoid mess,” says Tyler Browne, a 34-year-old who owns a cannabis vaporizer store in San Diego.

Djordejevic has heard from others who had more positive experiences with cannabis in their teens, when they had fewer responsibilities and began to get anxious when they smoked it as adults. Some began enjoying it again later on, once they became more settled in their lives.

In addition, it’s possible for the cannabis someone’s getting itself to change over time. “The different medicinal chemicals in cannabis may vary with each plant or batch, or even in the same plant-based on location, possible contamination, loss of terpenes over time, and degradation of cannabinoids,” says Morgan. Overall, the pattern has been for cannabis to become more potent over time, Djordjevic says. Another factor that will affect someone’s response to cannabis is what other substances or medications they’re using, Morgan adds.

If you want to increase the chances that your experience with cannabis is positive and stays positive, Goldstein advises against overdoing it on the THC. There are hundreds of compounds in cannabis, with CBD becoming increasingly popular for uses like pain relief and relaxation. “Try a low dose and give it time to work,” she says.

You should also make sure you’re using a fresh, quality product from a reputable source, ideally one that’s analyzed for potency by a third-party lab unaffiliated with any brand, cannabinoids, and terpene profile, says Morgan. If the product you’re using is new or unknown, take a small amount and wait 10 minutes after smoking or vaping, 20 minutes after administering cannabis under the tongue, and 90 minutes after taking an edible or swallowed tincture, oil, or concentrate. Morgan also suggests drinking lots of water along with it. There are also products like Undoo soft gels that claim to reverse THC-related paranoia and other adverse reactions, though they have not yet been proven or tested.

It may help to ask yourself whether you’re in the right state to use cannabis, Morgan adds. For example, if you’re trying to avoid or escape something, it’s possible the cannabis could just cause you to stress out about it more. Take note of whether particular strains or methods of administration tend to cause you problems, and stop using them.

“If you have easy access to dispensaries that sell small amounts, try different types and write down what you liked and didn't,” Morgan advises. “It’s no different from ordering the same dish at different restaurants or different menu items at your favorite restaurant. In general, responsible cannabis use with other trusted people results in a good experience.”