A recent study published in Neuron, a prominent neuroscience journal, showed a promising connection between habit forming and the endocannabinoid system (ECS). The research was led by Christina Gremel, an assistant professor of physiology at the University of California San Diego. The study showed that endocannabinoids, neurochemicals in our body that are similar to cannabinoids found in cannabis, allow for habit to take control of our body's action. This redirects our body from a goal-directed action to a habit, which we have preformed many times, such as brushing our teeth. It was already known that the ECS played a role in many parts of our bodies inner workings, but this study shows a new breakthrough in how important the endocannabinoid system is to our overall body function.
Earlier research by Gremel focused on the orbital frontal cortex (OFC), which is important for relaying information related to goal-directed action. When researchers increased the number of output neurons in the OFC using optogenetics, flashes of light that turn on and off receptors in the brain, they found that goal-directed action increased. When they decreased neuron outputs, the OFC was subdued and habit took over. This previous research served as a base for the understanding of how the OFC is connected to habit and goal-directed action, which was an important component in the study that showed the connection between the ECS and habit formation.
The study related to the ECS was conducted using trained mice, which pushed a lever for a food reward. They placed the mice in two different environments, one that was goal-directed and one that was habitual. The mice were able to switch between the two environments with relative ease, much like a human can switch between habitual action and a new task they set out to do. For example, the difference between the habit of getting home or the goal-directed action of getting to a new location not previously known. The researchers hypothesized that cannabinoids may be responsible for quieting the OFC, because they're known to reduce neuron activity in general, allowing habit to take over in the brain.
To test this hypothesis, researchers deleted the CB1 receptor in the orbital frontal cortex-to-striatum pathway. Mice missing the CB1 receptors weren't able to form habits, showing the critical connection between the ECS and the neurochemicals that travel along the pathway. It can be concluded from this study that without the ECS stimulated by internal cannabinoids, the consequences could be great, because they couldn't form habits.
“We need a balance between habitual and goal-directed actions. For everyday function, we need to be able to make routine actions quickly and efficiently, and habits serve this purpose,” said lead researcher Gremel. “However, we also encounter changing circumstances, and need the capacity to ‘break habits’ and perform a goal-directed action based on updated information. When we can’t, there can be devastating consequences.”
This study could prompt exploration into a new therapeutic use for marijuana for people with OCD or addiction problems. If the endocannabinoid system is deeply rooted in habit forming, and being able to break from habits based on a goal-directed action, it could aid in decreasing over-reliance on a particular habit. The body's own endocannabinoid system may need to be treated in some way to restore the ability to shift from habits to goal-directed action.