Researchers in the Netherlands have concluded that the THC potency of marijuana used by consumers does not reliably predict their risk for marijuana dependence. The amount of THC consumed, whether from low-potency or high-potency sources, also did not tend to indicate a person's chance of marijuana dependence.
Peggy van der Pol, a doctoral candidate at the Trimbos Institute of the Netherlands Institute of Mental Health and Addiction and her team decided to investigate the commonly held belief that marijuana smokers who use higher potency varieties will adjust their smoking pattern to use less marijuana.
The researchers looked at 98 young adults referred from coffee houses who all smoked marijuana at least three times per week. They were interviewed eighteen months later, and again in another eighteen months, as the participants were asked to smoke a joint. The team documented the time and length of their smoking behaviors and analyzed the potency and amount of marijuana smoked
While they did find that the tokers using stronger varieties did inhale less smoke and smoke slower than the tokers using weaker varieties, that did not fully moderate for the increased THC potency. "So users of more potent cannabis," van der Pol explained, "are generally exposed to more THC."
But, surprisingly, the team found that exposure to more THC by itself didn't reliably predict people's dependence on marijuana. It was more the way the consumers toked that determined who would match dependence criteria. Those who smoked more of the joint and smoked it faster, regardless of potency, were more likely to exhibit signs of dependence.
There is still much research to be done. This study covered mostly young males and the joints they were using, as the Europeans do, contained tobacco as well. Much of the participants' marijuana use was self-reported with no way to verify it over the three-year follow-up. There was no way to measure the effect of sharing joints with others affects the participants' rolling of a "typical" joint.
Of course, the biggest question is "what exactly is 'marijuana dependence'?" These researchers got that determination from the DSM-IV, the diagnostic manual for mental illness. Its seven criteria for cannabis dependence include tolerance (you need more to get high), withdrawal, using more than intended, wishing to quit but can't, spending lots of time dedicated to getting pot, giving up work and play activities for pot, and continuing to toke when you know it is causing you problems.