FREQUENTLY ASKED QUESTIONS
1. Cannabis, marijuana, weed, pot…are they all the same?
These terms have different histories. As far as this website is concerned, they all identify the same substance. We stick to the term cannabis. It is the biological term, the name of the genus that includes the wide range of various plants and products relevant to the studies covered on this site, and the term that has the least checkered past.
2. Why focus on adolescents?
The human brain develops a great deal during adolescence. Neuroscientists have also shown that the brain continues to undergo substantial development until around 25 years of age. Many jurisdictions base the legal age for cannabis use on their definition of adulthood—often 18 years. Some jurisdictions are weighing the evidence around brain development and considering 21 or 25 years as the legal age for use. It is important to note that the definition of adolescence used by neuroscientists refers to the period of time beginning with puberty and ending with a socially demarcated age of independence.
3. What is neuroimaging?
Neuroimaging, also called brain imaging, allows us to observe the structure and function of the brain. MRI, or magnetic resonance imaging, is one of the most popular and well-known imaging techniques used to observe the structure of the brain. Functional MRI, or fMRI, measures blood flow in the brain and identifies which regions are consuming the most oxygen. EEG, or electroencephalography, records electrical activity from brain cells.
4. What can neuroimaging tell us about the effects of cannabis on the brain?
Neuroimaging lets us know how cannabis use is associated with differences in the structure and function of the brain. For example, it can tell us whether cannabis users and non-cannabis users differ in the size of a particular brain region, in how ‘active’ that region is, or in how brain regions communicate with each other.
5. Do these studies show the effects of cannabis use, or only things that cannabis use is related to?
Distinguishing causation from correlation is vital in this field of research. For example, a study may show that cannabis users are more likely to be depressed. In this case, cannabis use could cause depression, depression could cause cannabis use, or another factor could cause both cannabis use and depression. Most studies take additional measure to come closer to detecting causation. For example, if a study measured cannabis use at 16 years of age and depression at 20 years, the time difference helps establish the direction of the effect. Researchers could also account for issues such as socioeconomic status to rule out these factors as a driver of the effect. The study summaries on this website point out these important aspects of study design.
6. Can we generalize results from these studies to the wider population?
The more people in the study, the better the results generalize. The closer the study participants resembles the wider population you are interested in—for example from the same province, age group, or socioeconomic status—the better the results generalize.
7. What is a meta-analysis?
A meta-analysis combines the results of multiple scientific studies. Each individual study has some degree of bias or error. By combining the results, a meta-analysis generally reduces this bias or error and provides a more reliable result than a single study can.