For many of us, coffee is a prominent fixture in our daily routine. Although we may not realize it, caffeine is the most widely consumed psychoactive substance worldwide. Fueling our early mornings and late nights, we can always count on our caffeine fix to get us through. However, despite its prevalence research regarding the effects of caffeine on the human brain is still lacking in many areas. Hot or cold, blended or brewed, cafe bought or homemade, our morning cup (or cups) of java may play a larger role than we think. A recent study conducted by Magalhaes et al. (2021) intended to further the current research by investigating the effects of chronic caffeine consumption on the human brain and its networks.
More specifically, the researchers conducting this study were particularly interested in the ways in which caffeine may affect the functional connectivity of the human brain and its regions. Functional connectivity (FC) refers to the interrelated relationship between spatial regions within the brain. It is measured using a non-invasive neuroimaging technique known as Functional Magnetic Resonance Imaging (fMRI). This imaging technique works by detecting changes in blood flow in specific brain areas. Active brain areas require more oxygen, and the increased oxygen concentration in those areas highlights the precise areas that are affected. In this study, participants underwent a resting-state fMRI (rs-fMRI) which evaluates interactions in brain regions without the participants completing any specific tasks. Subjects are merely asked to lay in the scanner for about 10 minutes and allow their mind to wander freely.
For the purpose of this study, a total of fifty-six participants were recruited and subdivided into two separate groups based on caffeine consumption habits: coffee drinkers (CD) and non-coffee drinkers (NCD). The CD group consisted of individuals who regularly drank a minimum of one caffeinated coffee per day, while the NCD group consisted of individuals who reported no regular coffee drinking habits, drinking less than one cup per week. The participants were interviewed and then underwent an MRI session before completing a second rs-fMRI session. Roughly 30 minutes prior to the second session, the NCD group was instructed to drink a 50ml Nespresso Ristretto coffee (highly concentrated espresso shot).
Results of this study revealed a decrease in functional connectivity in both the somatosensory and limbic networks in the CD group. The somatosensory cortex is an area in the parietal lobe of the brain, which is located toward the top of the head. It is responsible for detecting sensations such as touch, pain, temperature, and proprioception (where your body is in space). The limbic system, on the other hand, is located in the middle of the brain. It consists of several other structures that are responsible for processing sensory input and regulating our emotional responses, particularly in regard to fear, anger, and anxiety. Interestingly, these same results were observed for those in the NCD group after consumption of a single coffee.
Decreased functional connectivity was observed in other areas that are crucial to the vitality and functioning of the brain in everyday life. Specifically, FC was compromised in cerebellar, striatal, thalamic, and motor cortex regions. Although located in different areas of the brain, these structures all share common functions in regard to the planning and control of voluntary movements as well as the coordination of motor activity, in addition to other necessary functions.
Lastly, the researchers also wanted to provide a link to other neuropsychological dimensions by investigating the levels of stress, anxiety, and depression among participants. It was found that habitual coffee drinkers displayed higher indices of stress in comparison to the NCD group. Perhaps unsurprisingly, levels of stress were found to be positively correlated (both increasing at the same time) with the number of caffeinated drinks consumed. Individuals in the CD group also exhibited higher levels of anxiety, particularly in male participants.
This study adds to the existing research on brain function and caffeine consumption while taking a whole-brain approach in order to investigate the dynamics of FC in the human brain between habitual coffee drinkers and non-coffee drinkers. This study highlights the areas in which functional connectivity has been affected, thus providing a solid contribution to the understanding of the caffeinated brain and the ways in which specific brain areas may be affected.
Magalhães, R., Picó-Pérez, M., Esteves, M., Vieira, R., Castanho, T. C., Amorim, L., … & Sousa, N. (2021). Habitual coffee drinkers display a distinct pattern of brain functional connectivity. Molecular psychiatry, 1-10.
