November 13, 2011
What science says about addiction
Addiction is a serious problem in Canada-10% of the population affected, 20% of deaths related to addiction, 10% of hospitalizations, and a cost of $40 billion a year. It was the topic of a lecture at the Royal Ottawa Hospital on November 4, where Dr. Marco Leyton spoke. He is an associate professor at McGill and president of the Canadian College of Neuropsychopharmacology.
Citing various studies, Leyton outlined the relationship between usage and dependence of various substances, along with average age at first use and average age when the person becomes dependent. The results may be surprising for some of us. For heroin, 23% who use it become dependent. Typically, first use is at 18 or 19, and the person becomes dependent at 20 or 21.
Cocaine results in dependence in 17% of users, with first use between 19 and 22 and dependence from 23 to 25. For alcohol, 15% of users become alcoholics, with first drink at 15 or 16 and dependence at 20 or 21. Amphetamines give us a figure of 11% who become dependent, with dependence from 19 to 20. Only 9% of cannabis users become dependent, with average first use at 16 or 17 and dependence at 17 or 18. Yet it is marihuana that has created the high level of concern.
Leyton did not give the data for tobacco addiction, but the figures go through the roof. A New Zealand study found that over a fourth of smokers “started losing control” after three or four cigarettes, 44% after between five and nine cigarettes.
He showed the audience radiological demonstrations of actual changes in brain function associated with use of cocaine, amphetamines, and alcohol. The change is related to an increased production of the chemical dopamine in the brain. Dopamine is a neurotransmitter, which can initiate voluntary movement and regulate behavior in response to rewards/pleasure. The same response can be created by “reward cues”. Thus, for cocaine, the presence of the “fixings”–spoon, straw, and razor blade–can induce the production of dopamine and give a pleasure response. This reminds one of Pavlov’s experiments with dogs.
Blocking dopamine by means of other biochemical agents may not be effective. He suggested that even in a low-dopamine environment a person might sustain an interest in the substance. For that reason, he thought that controlled availability rather than total abstinence might be more successful, at least in some cases. This approach is in line with the practice that has been termed “harm reduction”.
To lessen addictive behavior, it is also helpful to eliminate cues. Thus, we could extrapolate from his remarks, with cocaine, avoid having “the fixings” around. With alcohol, no fancy glasses. For smokers, no ashtrays.
Addictions are complex. More does not necessarily lead to more pleasure or to saturation. It depends, for example, on how much more and to the history of use. The issue is also confused by the involvement of another chemical in the brain, serotonin, which also has a part to play.
Addiction, like other human behavior, is a matter of environment and heredity. It is not surprising, then, that it tends to run in families. Not everyone is equally susceptible.
