Genes May Hold the Key to Overcoming Addiction

Studies into the genetic basis of nicotine cravings could one day help curb addictions to cigarettes; or even, potentially, other types of drugs.

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Have you ever wondered why some people are able to quit smoking while others try over and over again without success? The answer could be in our genes.

Rachel Tyndale, Professor in the Department of Pharmacology & Toxicology at the University of Toronto and Head of Pharmacogenetics at the Centre for Addiction and Mental Health studies the genetic basis of addiction. Her lab examines how the differences in our genes determine our individual reactions to the same drug. They also look at which genes are involved when a person first takes a drug, when they become dependent and when they try to quit.

In the case of smoking, Prof. Tyndale has shown that people who have more copies of a gene for a liver enzyme called CYP2A6, metabolize nicotine more quickly which in turn causes them to have stronger cravings for cigarettes. This helps us understand why the nicotine patch is not an effective treatment option for all smokers. For someone that breaks down nicotine at a faster pace, wearing the patch, which slowly releases nicotine into the bloodstream over a long period of time, will not quell their strong cravings.

Prof. Tyndale has also shown that variations of drug metabolizing enzymes in the brain can affect an individual’s response to opioids, like codeine. Most recently, her work in rats shows, that smoking may cause these enzymes in the brain to metabolize codeine more quickly than in non-smokers. In an age when abuse of prescription drugs is on the rise, identifying these genes could be the key to developing personalized therapies to overcome addiction, or even stop it before it takes hold.

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Professor Rachel Tyndale is a pharmacogeneticist, focusing on the genetic sources of variation between individuals in drug response. In the clinical area of addictions, this involves both the drugs of abuse and the treatment drugs. Her research seeks to identify and understand risk factors, and underlying mechanisms, in substance abuse and to implement genetic approaches to personalize treatment. Her laboratory program also has a major interest in understanding interindividual variation in drug metabolizing enzymes within the brain on effects of drugs and toxins. Dr. Tyndale sits on numerous scientific advisory boards, editorial boards and was chair of the NIH funded PharmacoGenomics Research Network ( She is the recipient of over 40 National and International awards in basic and clinical pharmacology. Dr. Tyndale received her BSc from Queen’s University, her MSc and PhD from University of Toronto and NIH, and was a postdoctoral fellow at UCLA. Dr. Tyndale is head of Pharmacogenomics at the Campbell Family Mental Health Research Institute, Centre for Addiction and Mental Health, the Endowed Chair in Addictions, and a Professor in the Departments of Pharmacology & Toxicology, and Psychiatry at the University of Toronto.